If you believe the web site, my nearest guitar center currently has 543 guitars in stock, some of which can only even be reached with a ladder. So if you assume one minute each to take them down, check the tuning, put them back, move the ladder, etc., you're at about 9 hours. A fair bit of that time will be spent just to see that it's already in tune anyway.

And Guitar Center in particular is in the phase of its life where private equity is pulling every dime out of the business until they can eventually just shut it down and sell the real estate, so they're not paying anyone to go tune guitars. You're lucky if they're paying someone to clean the bathroom.