GMs are supposed to limit looting as much as possible, within reason. Picking up a few guns or some ammo, no big deal. Stealing every vehicle, drone, and stripping down multiple bodies for cyberware? That starts to become an issue.
One of the reasons is that we're attempting to maintain a certain balance among the characters. Without levels or anything else to put a limitation on what characters play what games, certain things can start skewing the balance of a game really, really fast, even moreso than karma. Especially if heavy duty weapons, gear, or cyberware are nabbed.
Another is time. Some players have, in the past, gotten a bit... loot happy. To the point where it was actively detrimental to the rest of their group and to the game as a whole as they start running around trying to find ways to steal everything that's not nailed down, rather than focusing on completing the Mission (And in a convention setting, with under 4 hours when you might be playing with 5+ strangers, this can be a problem).
Looting is generally allowed within reason, but players shouldn't be steal-happy. That's not really the point, and it forces the designers to start reconsidering how we present adventures and even the rules for Missions as a whole. There's a reason we enforce some pretty strict fencing rules, for example. We don't want "loot inflation" to destroy the Missions game balance. We write and design based on X karma and Y money, with Z additional revenue picked up here and there. GMs will tweak as needed, but the less they need to tweak, the better. And the less a newer, starting character feels outclassed, also the better.
Pathfinder Society is something we've been watching carefully, and it's been suggested to us numerous times (by both GMs and players) to adopt something similar to their method, where straight-up you don't keep anything you loot. Instead at the end of the adventure you get a set amount of bonus cash, and you can spend that on specific items that appeared in the adventure. This allows for multiple characters to end up with that +3 sword of ogre slaying that one enemy had, for example. It also prevents characters from managing to acquire the "Vorpal Sword of God Slaying and World Devouring" that was the McGuffin the boss monster had. This is something I'm seriously debating instituting.
I'm avoiding it for now, hoping that our players are willing to be reasonable and that our GMs can keep things moving and out of their hands... But frankly it really sucks that I have to seriously considering giving NPCs any expensive gear to help make them more of a realistic challenge, simply because I know PCs will go "Look! Expensive Cyberdeck! Attack Chopper! Rocket Launchers! Wired 3! Steal it alll!!!!!!!!"