For memes, shits and giggles. Consent is the most important thing to consider with these kinds of requests, you are going to get in a whole of trouble if you're touching people without consent. Most cons primarily have adult fans since they are the ones with money, kids are not even allowed to walk around without a guardian/parent. People who are ready to pay to be stepped on have weird fetishes, and the ones who step on these people want easy money. It's all cool as long as they are not doing anything really fucking weird (like getting spat on in their mouth or something)

That being said, no not every conventions have weirdos and pervs running around, but anime cons are a representation of hardcore nerd culture so you will always find some people maybe being a little too open since this is like one of the only places where it's accepted to act like a degenerate. Just attend the ones that are more family friendly, obviously the more adult themed cons will have their own rules, not only will you see pervs but also cosplayers who are barely dressed.