Traditional Irish Music
I guess it is because they're very hard to learn, both to play and maintain, with 7 reeds humming in unison and all :)
Add to that waiting lists for up to 10 years, and prices you could get a decent car for i'd say it's no wonder, unfortunately.
I think it's fair to say that the main reason you don't see more sets of Uilleann Pipes at sessions, is probably the cost factor.
However, other factors do come into play too, like for example the tuning factor. Sure, most instruments, apart from fixed Reed ones like Accordions & Concertinas, require a certain amount of tuning, but be honest, nothing like the work a Piper has to exert, to keep all those reeds in tune with themselves, each other & the session.
As a Fiddler, I love to tune to a set of Pipes & I don't care whether they are in D, C, B or Bb or anywhere in between any of those options & no, I don't mind having to retune my Fiddle, as the pitch of the Pipes changes due to temp & humidity. However, I know lots of musicians who don't or won't retune for Pipes & others who actually call you snobs for even wanting to play in what they think of as unfriendly pitches & keys .... sad, sad people! :-(
One of the pure joys of Irish Music has got to be its diversity, which I think we should all revel in, not fight against, so I love playing along with Pipes, but I also know I'd never make a Piper, for they're a rare breed of really dedicated musicians & Irish Music is all the better for them being around.
I'd say thousands of people were turned onto Irish Music back in the 70s quite simply by hearing the sound of Irish Pipes for the first time with the group Planxty, so there is & hopefully will always be, a place for Uilleann Pipes in Irish Music.
The fact is, they were almost extinct, back in the 1940s, but since then they have become much more popular & I think it's fair to say that there are now more Pipers & more sets of Uilleann Pipes around, than at any other time in history.
OK so they're difficult to learn to play & expensive, but let's face it, if we all went for the easy cheap option, we'd all just be playing Tin Whistles & Bodhrans .................
Oh what a terrible thought, please excuse me, I need to go & lie down now, in a darkened room! :-)
I hardly think it's an accurate statement to say the the pipes are going out when there are more sets in the world and on more continents than ever before. Whether all of these sets are being played and being played well is another matter but the popularity is about as full as it could be expected to be. I can't imagine it being good for pipes to be as common as, say, the fiddle. For example, you show up to a session and there are three fiddle players... no big deal so long as they listen to each other and play well together. Now, you show up to a session that has three pipers... I can't imagine a scenario where that would be ideal.
In reality a nice practice set of pipes can be had for a few thousand dollars to an interested beginner. Furthermore, there are clubs around who keep loaner sets on hand to promote better accessibility to would-be learners at minimal financial risk. They are indeed a difficult instrument to learn and even more so if the learning does not take place at the feet of one who has already attained proficiency with the instrument. I'd say that a beginning piper has more information and tuition available than at any other time in the past. Between the online resources of NPU and various other organizations a starting piper has quite the wealth of resources. Of course, as mentioned above, none of this takes the place of learning from a teacher but in the worst-case scenario you have the option of Skype lessons.
The Uilleann pipes appear to be getting more popular, but I think there are three main reasons that they aren't as popular as they should be:
#1 Lack of awareness - Most people that are not very familiar with Irish traditional music genre have no idea what instrument they are hearing when they listen to Irish music and hear the pipes, even though they may love what they are hearing! I've spoken to many well-educated people in the U.S. who cannot describe what Uilleann pipes look like or sound like. I hope this changes in the future, as I personally consider it the most heavenly instrument in the Irish music tradition.
#2 Lack of students who can afford a set, and proficient teachers and players to provide training.
#3 Perceived difficulty and complications of learning and tuning the instrument. I think this may scare potential players away. I'd like to see more young children in the U.S. started on this instrument around the age of 9 to 12 years of age.
Chiming in late on this one, but I wanted to add to Connie's observations as a teacher and performer on the pipes:
#4 Even in good economic times, most parents are reluctant to spend even a few hundred dollars on cheaper instruments like guitars. Small wonder one sees few or no children playing the pipes in the United States.
#5 The majority of new piping students I encounter in the States are grown men and women with careers and families (and very little time to practice!). Most of them do not participate in sessions.
#6 The cost factor is due to the extremely difficult and time consuming nature of making them by hand. Pipemakers may charge a lot of money for their work, but they're not getting rich, believe me!
I enjoyed Dick Glasgow's comments, I like people who like pipes, also Connie's statement about perceived difficulty. I often hear that, "oh aren't they difficult to play". Well so is everything, I tried the guitar and fiddle and couldn't get the hang of it, pipes suited me better. It comes down to having an airtight set, good chanter reed, patience and finally God given or nataural ability. As for cost, I believe one can get a decent practice set for $1000 new.
Maybe Seamus Ennis, God rest him, frightened us all off with the old '7 years learning, 7 years practicing, 7 years playing' quote!!!