Unpopular opinion : I dont understand why people tip waiters

My understanding is that in the usa wait staff are paid very low rates because they can earn tips. In Australia I don't tip unless it's small change at the register going into a general tips jar or someone has been especially helpful, but it's never a large amount.

I'm more inclined to tip on Sundays or Public Holidays if I believe staff aren't being paid penalty rates for working on those days.