I, for one, am a positively mediocre sysadmin. And the amount of time I have to spend waiting for GitHub to fix bugs is almost certainly far, far, FAR less than the amount of time I'd spend scrambling (but not waiting!) to fix my own.
This is also how I feel about Heroku.
For whatever reason, I prefer the helplessness I feel while waiting for them to fix stuff to the helplessness I feel when I'm in "OH SHIT MY SERVER IS DOWN AND I DIDN'T EVEN DO ANYTHING AND WHY IS THE DATABASE NOT RESPONDING IT RESPONDS WHEN I QUERY IT MANUALLY AAAUUGGHHH!!!" mode.
Although I do try to keep myself sharp by doing things by hand in other areas of my engineering activities.