Having worked at a music store (not guitar center) you’d do that all day long if you tried. I swear, the first thing everyone does when they pick up a guitar, is start fucking with the tuning pegs (whether it’s already in tune or not).

A lot of times our sales guys would tune it real quick, while they talked about the guitar, before they handed it to potential customer.

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.

I wish they would at least throw in a setup and strings when you buy a new guitar...

In Japan all of the guitars in shops (no GC here) are tuned by a clerk when you are ready to play them. I'm pretty sure the strings are also slackened when they go back on the rack.

When I bought my guitar, I bought 3 extra packs of string and an electronic tuner tool. Tuning the instrument was the first thing I learned how to do with it. Seemed rather important to know, you know?