I run my E-6 myself because it is more convenient. Many of my shoots don't finish until some 2:00 or 3:00 in the morning and I just don't like to wait until the next day to get some of my film back. So, I'll run the rolls in my Jobos so I can get them done and ready. Plus, I can run my own C-41 for the same reason. I'll do the film here, then do a contact sheet, evaluate, crop and send the carded negs off to the pro-lab for final printing.
I do my own Ciba's, so I can keep my work in house instead of having to rely on some lab for a time schedule. The only time I send everything off to the prolab is for critical work, ie, weddings, etc.
If you've ever been non-methodical in your life, then you'd wanna be careful if you run your own colour film, sometimes, the absent-mindedness can get to you during a 6 minute segment of the processing cycle!