Better give everyone a 103% raise while they are at it.
Well, that's what will happen when you try a "one size fits all" law like this. The $15 isn't enough to live on in NYC. In much of flyover, skilled people like electricians aren't making much more than $20/hr, and they seem to do okay given the cost of living. Where I am, minimum wage is currently $7.25. I might argue that this is too low given rising expenses (thanks California!), but $15 would be too high. That electrician is going to (rightly) say that if the kid at the local diner is getting $15, then he's certainly worth $30, and he would be right, and then everybody's expenses to get stuff done goes up.
That 30 year old burger flipper that is taking the job of a High School kid is going to kill grandma on her fixed SS income.