If are one person short on a shift, then lose revenue. One person long, then waste money. Getting the staffing right, for each shift, for the year, is a LOT of money -- add it up yourself.
Net, there's a LOT of difference between running a good fast food restaurant and not. So, someone who knows how to run 10 such restaurants can be getting annual cash income over $1 million a year, with a VERY stable job, where they can't be fired and where they can bring their children into the business. Go to a yacht club, and it is mostly such people you will find.
The blunt point is, in the US, some of the best opportunities remain just doing well in a Main Street business.
Then, if some computing expertise can help, still better. But, generally in the US, getting away from just owning a Main Street business is a risky career direction.