I used to work at a shop about 20 years ago. It was expected that I take no more than 15 minutes to assemble a new bike. 12 if it was a single speed kids bike. They come mostly assembled, so we just needed to put the last few parts on, adjust the brakes and shifters, check the bearings, and check all the fasteners. We would spin the wheel and fix it if it looked horribly off, but I don't even recall if that ever happened my whole time there. Of course if the bike were for me, I'd want to be more picky, but my boss just wanted them safe enough to put on the showroom floor in as little time as possible.

While it's true that machine-built wheels are usually not perfect out of the box, they are almost always safe and rideable. They're usually spec'ed very safe as well (high spoke count, strong/heavy rim). Anyone touring or racing would likely seek an expert and pay closer attention to their equipment than the typical casual rider.