They have just given you a big part of themselves and they feel you don't have the decency to stay for even a few minutes and applaud which is their reward. In the grand scheme of a life, do 5 minutes of applause really make that much difference to the audience member, when it makes such a HUGE difference to the emotional health of a dancer?
I've known a few dancers over the years and agree with LMCTech. Not to get too dramatic, but most dancers seem to be in fear of "the injury." Although they have their nagging aches and pains, they know someday they might do something that will end their career. And it is sometimes stupid stuff: a partner knocking you off your leg and breaking an ankle. Slipping on a pile of Nutcracker 'snow' and twisting a knee. Going for it in a 5:00pm rehearsal and pushing through the 8pm show with nothing left - only to tear up a hip. In the matter of a few weeks, SFB lost Joan Boada, Nutaree and Tina LeBlanc to injury.
These dancers literally put their bodies and careers on the line for us every night. Can't we audience members at least have the decency to sit for 5 minutes and show our appreciation?