If the mechanics in your area do this, you have some crappy shops near you.

When I worked as a wrench, and encountered a gummed up shifter, I would do the troubleshooting/cleaning, and charge them for my time. When they picked up the bike I would explain what was done to fix it, and show the customer how to do it if they ever had the problem again. I'd do the same for any flat repair customer.

Some people don't want to mess with doing simple repairs, but some do. It's their choice IMO.