No dance pants allowed

Maybe I wasn't paying close enough attention all those years ago, or maybe times have changed. But the Irishettes seem to have a particularly micromanaged practice wardrobe.

Members must be dressed properly for each practice.  Practice clothes include shorts with tights underneath and tight fitting sports bras with tank tops.  NO DANCE PANTS WILL BE ALLOWED DURING PRACTICE.  Pants, t-shirts, and sweatshirts will be permitted throughout warm-ups, but MUST be taken off when dancing begins.  Each dancer is required to have both their jazz shoes AND a pair of supportive tennis shoes at every practice.  Knee pads are optional.  All hair must be back and out of dancers’ faces during practice.  NO GUM will be permitted at all during practice.  NO JEWELRY will be permitted either, with the exception of stud earrings.

What are dance pants? And why are they forbidden?