Many restaurateurs have been running restaurants and cooking professionally for years before they try to open their own. I'm not sure writing software is as helpful experience wise.

You would be surprised. It's an extremely competitive industry, with some very hard-working people. And hard work is no guarantee of success either.

What strikes me as recurring problems from the things that make it on to shows like Kitchen Nightmares are the following.

  * Can't or won't keep the accounting books in order.
  * Micro-management of staff that want to do the job.
  * Under-management of staff that aren't doing the job.
  
  * I /suspect/ not paying the staff enough (in money/respect/etc) to keep good staff and keep the motivated.

Unfortunately the real world is not like Kitchen Nightmares. Often restaurants with good management still fail due to other reasons, the margins in hospo are razor thin, it doesn't take a lot going wrong to go out of business.