In my opinion, from a practical standpoint… it’s that it doesn’t matter what you just ate or drank, you can still play without ruining a reed or having to clean out the bores.
And… they sound nice.
They store well. 
Never having to say “I’m sorry” or “I love you”.
That they’re always in tune and seem to play almost automatically with perfect timing.
You can play Irish music with a decent instrument without having to learn the fiddle…
I like this answer Oliver !
but here is my own best thing about the Pipes; they have kept me away from my boring Day Job and, usually, fed and watered, for the last 37 years… 
So, thankyou Pipes and thanks to all my customers too!
Geoff. 
Touché! And fair play to you! 
The pipes teach me the true meaning of despair and frustration.. Truly a learning experience…at the moment I HATE THE B’ STARDS 
You can smoke and play at the same time! WOOOO!!!
On a more serious note, I like how you can sort of improvise or spontaneously embellish the music while you play, sometimes creating happy accidents. The mistakes such as squeaking squawking notes and missed or jumped octaves from said spontaneous playing make it all sound more beautiful IMHO.
They have a safety belt.
Some of the great people I’ve met: pipers, pipe makers, and non-pipers.
You can play quietly in the back and SUDDENLY get louder. 
The groupies; chicks dig them.
What everyone else said plus the fact that its a stand alone instrument in that, you have your bass section (drones) your rhythm section (regs) and the solo part (chanter).A veritable orchestra right there on your lap.
RORY
You’re not expected to wear a kilt.
Busking on the street and hearing people try to pronounce the name to each other 
(you can’t call them “union” pipes in the southern U.S., people will think they are crossing a picket line…)
dave boling
The C natural!
A High E bent up from a Ghost D.
And BCD Triplets.
The buzz, and the buzz you get from playing them! 
The best thing about Uilleann pipes is you don’t have to take a hit in price should you be forced to sell pipes made by a reputable maker !!