A slippery floor can cause injuries but a sticky floor can cause injuries too especially to knees. The person hosting the dance needs to do a risk assessment to determine if the floor is too fast or too slow. Too fast may lead to falls, too slow joint injuries. By inaction either way may lead to legal action.
Let's say you did a risk assessment by dancing on the floor before the event and you find it sticky. By hiding behind "We are not allowed to put anything on it" may not protect you at all against legal action, you knew it was sticky, you know people will get sore knees but you did nothing even though you have a duty of care.

Some uncaring person somewhere has determined that legal action is more likely if someone falls rather than gets twisted knees so let's keep it slow?

The real problem is that suitable, predictable and effective "floor toppings" don't seem to exist. Sawdust (eg. Pops) make the floor inconsistent, slippery in places and still sticky in others. Wax can be OK after the dancer has had a few evenings on wax but initially its like dancing in stiff mud!

My feelings is that you only use venues that have a suitable floor and don't try to modify a bad floor, suitable products don't exist. Most importantly clean the floor very well, every bit of grit causes problems. Always do a risk assessment before the dance and sign-off. If you feel its OK but a little fast then warn the dancers. If you do a risk assessment and someone gets hurt then you are in a much better situation than no risk assessment.

I sometimes use baby oil on my soles on a fast wax floor to slow it down and have one pair of shoes with the reverse leather and another (for fast floors) with thin cork sheeting glued on the soles. This cork sheeting (gasket sheeting) can be found in auto shops and is cork impregnated with neoprene rubber, excellent for fast wood floors.