This is most likely the case. I can't think of any reason other than the fact that financially, the shops don't think you deserve a properly adjusted hub unless you spend a minimum dollar amount. They've lost touch with, and respect for that particular model's customer base.
Skipping hub adjustment tends to become a habit that's hard to break, so eventually, they don't bother adjusting any hubs at all, assuming anything over their minimum dollar amount has already been properly adjusted from the factory. If skipping this step saves time, they find even steps to skip to save more time.
I find it easier to take the one minute to adjust every hub. If this one minute adds up enough to endanger a shops financial status, they have bigger problems, problems which are more closely related to their philosophy on how price point=whether a customer deserves a properly adjusted bike.