Seems like a compliance thing? I too run my LLMs inside some sort of containment and does "manual" development inside the same environment, but wouldn't make sense to have that containment remotely, so I'm guessing that's because they need to have some sort of strict control over it?
While there are compliance/security benefits it is not the primary motivation.
If you have fairly complicated infrastructure it can be way more efficient to have a pool of ready to go beefy EC2 instances on a recent commit of your multi-GB git repo instead of having to run everything on a laptop.