There aren't a lot of big businesses that start at MW. I have multiple tax clients though that run small successful businesses that pay close to MW to start. I think one pays $7.75 for kids to work at her shaved ice stand.
The kids that work there just want a summer job and don't have any experience. They aren't going to get a job anywhere else. It is great experience for them and the prices are dirt cheap at the shaved ice stand. The owners pay the bills and get a little bit of income from the stand. Not a ton.
If wages went to $15, they wouldn't make it. Their prices would nearly double just to get by and their profits would drop. It wouldn't be worth it.
I can think of at least 2 other small businesses that employ kids with no experience that would be hit hard and might not make it.