Most folks have already hit the highlights like Linux support, customer service, pricing, etc. another I haven’t seen is the toolkit for devs and server hosts. I host a ton of game servers, and for most steam games it really is a trivial cookie cutter application of steamcmd to get a Linux dedicated server up and going. And because the devs built for the platform, the admin features all often use simple steam IDs for game permissions, making it easy to manage that functionality as well with a group of friends.
Basically, a ton of things just work consistently. Not to mention the pricing and early access fosters a lot of creativity. And my barotrauma, enshrouded, ut2004, TTT, prop hunt, vrising, etc servers are all basically an identical launch config with a slightly different appid and it all just works.
You don’t get that from the pirated versions or from gog generally.
From a security perspective, if two people and the luggage clear screening, and one ticketed person proceeds to fly with the luggage, then it doesn’t matter which one of them it was, right? I’m sure it’s against the rules and the airlines might care. But just gaming the scenario out, I don’t see how a pre-screened gate visitor changes the security posture as long as one of them boards the plane with the luggage.