This is a fascinating topic and one that should not be taken lightly. There are a number of emotional and 'technical' aspects to founder retirement. 

When you have created or significantly grown a business, it becomes part of your identity, part of your purpose and letting go of this can be extremely difficult. 

It doesn't matter how logical it is to move on and transition someone else into the business, be that family or not, the emotional aspects of doing so are all too often overlooked. 

This article highlights this with real life examples.  

Also, check out this podcast from The Family Business Podcast on this very subject.