I would think, but those costumes generally take a bit of time to get into, and everybody
visible in a scene has to wear them, so you can't just have random people in the background. That also limits filming locations to spots where no outside people or bulidings are visible in the background, which can be especially troublesome if you're shooting lots of overs and need the background behind both conversing actors to be consistent with other wide-angle shots of the scene.
Setting the show in what looks like a modern period gets rid of that, and opens up any city, small town, or rural area as a filming location. The one snag to deal with in the storyline is cars, which on most sci-fi shows set in the future need to look both different and "futuristic."
car to look halfway believable as a future model is difficult, and unless CGI is used to fill in the background traffic (or flying cars, of course), any production would need dozens of futuristic cars. As far as I can remember, Stargate avoided that whole problem by never
having cars on other planets. (Can anyone remember an episode with aliens in cars?)
That can be an important piece of backstory for the new show. We populated hundreds of alien worlds, and not a darn one of them had cars. We couldn't use Goa'uld, Asgard, or Ancient car technology because they didn't have any, either, darn the luck.
So when we expanded into the galaxy, we just had to take our cars with us, jeeps and Hummers at first, and then road vehicles once we started building roads. Since shipping gas through a stargate is also inefficient, and since almost none of the planets we were settling had decades of exploration geologists hunting petroleum reserves, we started sending electric cars and more Naquadah generators to support the grid. So the production company can go buy or lease a bunch of Nissan Leafs, Chevy Volts, Teslas, and whatever else is on the market and write them off as an expense. They'll keep showing up on just about every planet the SG teams visit.
But as the off-world populations expanded, demand increased to inconvenient levels. Since shipping millions of cars through the Stargate system is inefficient, if not downright stupid, we made duplicates of our car factories and shipped the tooling. So every planet ended up with couple of early 21st century car factories and just kept on making the same basic designs. Being planetary monopolies, none of them really faced any competition, anyway, so there wasn't much push to change what worked, with occassional retro-styling coming and going (like the new Mustangs and Camaros) as local oil reserves were finally developed.
The show could even play with the mix for comedic affect, kind of like recurring jokes about cars in the old Soviet union. Jack O'Neill, early in a typical episode: "And today, boys and girls, we're on the Chevy planet. Gotta love Chevy." Sgt: "That's what you said about the Ford planet." Jack: "And it was just as true there."
That highlights another odd advantage this show might have. With the rising use of DVR and other technologies, commercials are often getting stripped. In saving production costs by leaving lots of everyday items the same, centuries later (perhaps with clever tweaks), it is a perfect vehicle for product placement.
Product placements can't be stripped by DVR's, rips, or any other means, and that might be a strong selling point with advertisers who'd rather have Jack or an alien talk endlessly about the durability of a Ford F350, proving itself over centuries, than airing a Ford F350 ad that would get stripped by everybody's DVR's anyway.
The placements would even be in the season box sets, forever and unchanging. That's a potential selling point to the network suits, as this would be one of the few shows where the characters could consciously talk
about existing products with amazement, even discuss them with awe and admiration (You're still using these! -- Yes, those are the most useful thing we brought through the gate!), without the whole scene looking ridiculous and forced.
Lower production costs, higher revenue (hopefully).