I was so confused at first, but now I understand!
Yes, I was never saying cheerleaders shouldn't wear bras/underwear. In fact, I'm a card carrying member of the bra brigade.
My cp is also a dancer and at every studio she's been at and the ones we know their policies, dancers aren't allowed to wear underwear under their shorts or leotards, with maybe the exception of a sports bra under a leotard, if you have a nice ballet mistress/master.
I don't even know if I've told this story here before, but my cp started cheer after dance, so she was used to following dance rules and didn't know that cheerleaders wear undergarments. Luckily, we were blessed with an amazing cheer big sister; who quickly notice her little sis was missing a key item and then pulled us both aside, in the middle of practice, to fill us in about how the two world were different on that department! I'm forever grateful to her for being so quick and discreet about it!