For every "literally five minutes" job shortening cables on a well maintained bike, there's 4 other "why won't it shift, and what's the cheapest I can fix it for" jobs in the queue; the argumentative pricks who buy a dusty, rusty, squeaky, non-shifting, barely rolling bike they bought for $10 at a garage sale and then get pissy when you explain that it will cost $150 in parts and labour to fix it up, and that's lowballing the time.
It all balances out in the end.