Because there are deals to be had.
Ruger Mark IV Hunter has an MSRP of $999.00 That's w/plastic case and 2 mags
Gun Broker sales range from $631.00 cardboard box one mag, to $819.99 no mention of box or number of mags. All these were the same Hunter model, stainless, with basic wood grip, fluted barrel, and fiber optic sights.
At KTP on a "Ruger Day" I paid $275 for the same model in plastic case with 2 mags, and got a store credit that covered a couple more mags. And I would have bought a target model too, but they were sold out. People were lining up for the Rugers, I'm sure some were just flipped. KTP was limiting per person sales.
I won't make a trip for it, but if I'm going I'll also go through their bin of used mags, can usually get a few S&W 59 or 39 series mags, Barretta 92 mags are also common, and I scored a couple Walther PP mags too. Hard to beat that 10-15 dollar price.
So there are times going there makes a lot of sense.
Minus a special event I would go there for a new gun, but I will always stop in if I'm already in the area. That will change if they put in a wait.