If youre working with a client in a rehabilitative or wellness regime, no.
If their aiming to lose weight or get better athletic abilities, you are challenging them to the best of their capabilities.
Yes, get a weight belt for someone who maxes out on squats, deadlifts or upright rows.
Dont get a weight belt for you 8am 40yr female client.
Everything has a place in the gym, you simply need to take into account who youre working with and what their goals are.