Firmware build times can be comically bad. Most firmware builds are heavily optimized and you often build the same codebase dozens of times with each build optimized for one particular hardware configuration of many. You then get to deploy to a legion of test devices (also managed by machines you remoting into) and see which special snowflake you managed to break this time (it somehow is never the one you sanity checked your changes on during development :-D).

It's common to throw (a lot) of compute at the problem, and at some point it's way nicer if the 100+ cores you're cranking to 100% CPU for a few min are somewhere you're not sitting next to. It's also nice that those resources can be shared among many devs so they don't sit idle most of the time.

So, you end up with the thin client pattern. It's usually practical to build locally as well for a few particular targets, which might be a random dev board at your desk. But if I have a remote build system with a few hundred cores cores and a few dozen TB of ram, why would I not just use it instead of using my laptop?

Athough firmware and hardware is such a huge, varied field many people likely have different experiences. Brining up a big custom SoC is way different than bringing up a board with an FPGA and all off-the-shelf stuff.

What's "far more than ssh to some remote server" mean to you? It's always fascinating how different everyone's experiences are.