Even worse, they have to pay taxes in every state they play in because they're working in that state. It's called the jock tax.

https://en.m.wikipedia.org/wiki/Jock_tax

That's not that unreasonable... they're working in the state, they should pay income tax for the work they do while in the state.

Many (but not all) states have tax credit arangements with other states so you wouldn't pay full tax on all income to your state of residence as well as the taxes owed to the states you worked in.