"There are some things I do myself and some that I prefer the shop to do. Therefore I tend to put the bikes in the shop once a year for a full service, and keep it fettled myself in the meantime."
But what do they do at the "full service" that you can't?
For me...although not in a service, these are jobs I will not tackle
Tune my wheel, I don't have a spoke tension meter or a good ear for a tune so will not attempt a wholesale spoke tightening / wheel straightening on my own for fear of adjusting ALL my spokes to a too high a tension....I will adjust individual spokes but not a whole wheel...I get through a rear rim a year.
Bottom bracket lube, no tools for the job and I hate the idea of buggering up the tread on the frame.
Servicing shifters, like actually opening those suckers up.
everything else I am happy to do.
However, I don't share your view, it feels a little elitist, like telling people they should't ride if they cant service their bikes. I drive a car and a motorcycle...I even use a loo occasionally and I don't know how to take any of them apart.
I prescribe to a view that its better to support my LBS, even if they make no money they retain loyal customers who, like me, spend far too much cash in their shops, often under their recommendation.