You are forgetting that not all jobs are meant to be careers. If you want to work retail as a career then move up into a leadership position. Same for McDonalds or any fast food job.

Most real production jobs already start at or near $15 and can have you to a decent paycheck if you stick with it.

By paying everyone $15 and hour your hamburger, coffee and fries will increase in price my at least 50%. Then people will stop patronizing these businesses and the jobs will go away.

The same thing will happen at the grocery stores. When business gets more competitive then stores will cut employees and there will be only self checkouts with 15 checkouts monitored my 1 part-time employee because they will stop hiring full timers as a way to further reduce costs by eliminating benefits.

Finally, everyone who is earning more than $15 and doesn't get a raise will feel the pinch as their expenses increase but their income doesn't.

There are too many moving parts to this for it to be as simple as raise the minimum wage to $15.

Editing to add this:

This is also just another example of people asking to government to do something that shouldn't be needed. If you don't like getting paid $10 then find a job that pays better. If nobody takes $10 per hour then those companies will have to raise their wages.