I DESPISE mandatory tips. And 15% is standard, not 18% and CERTAINLY not 20%. And, most of all, a tip is for good service, not for continuing to breathe.
Maybe it depends on where you live, but 20% is considered standard for tipping now, and has been for about 10-15 years.
But I agree it should not be automatic.
Ever since minimum wage for workers, the girls at the local diner make $18 an hour. I quit tipping. They do 10-12 hour shifts. They make more than I get on retirement.