Don't these places keep their own source?

There've been some cases of remastering projects being affected by the loss of some of the source material, such as the Silent Hill HD Project

Which is why I find the negative attitude of so many of these companies toward emulation and fan conservation of abandonware so frustrating, there's a proven track record that they cannot be trusted with the task.

Microsoft used pirated software to create some windows sounds back in the day

https://www.techrepublic.com/forums/discussions/windows-uses-pirated-software/

people only care when they're told to and are being paid to. If nobody told anyone to care about the archival of source code (and build environments) of old projects, then guess what, it's not likely that anyone is going to do it. Add some good old revolving doors and presto: shit's fucked

Even if the source is kept decently preserved, the build environments are usually not. If they still have a machine in the exact state it was in at the time the game was finished, it might be as easy as Project -> Build, but... they almost certainly don't. So that likely has to be rebuilt from scratch, and you'd be very lucky to find any kind of documentation on how things worked.

Game studios tend to have it particularly bad because of how much binary-only engines/middleware (standalone bits like Havok physics/Bink video/etc) they used, how often the game's data and code builds were mixed together in some way and how in some cases the project is designed to build things like console releases at the same time. If you lost the install files for your physics engine, you're probably straight up screwed.

By the time you've figured all of that out, you can be easily hundreds of hours in, with tons of weird little issues that might require different people to solve. Some examples: you might end up needing to build it in Windows XP because no other OS runs all of the software used during the build, any sysadmin is NOT going to be happy installing WinXP on their network so the machine has to stay offline, getting code onto that machine might be a pain due to how Perforce or whatever is used by them, even things taken for granted like a particular version of the DirectX 9 SDK might be hard to find, etc. Sometimes licensing/activation of tools used in the build process is an impossible to solve problem because it needs some DRM dongle or activation server that no longer exists and the software was never publicly available, so there is no crack.

I would imagine more bureaucratic processes being the issue here. I can imagine some Rockstar employee tasked with getting the game up on Steam, trying to get the game through official channels to put on Steam, getting frustrated, saying f-it and downloading the Razor 1911 version thinking they removed all the references and then pushing it to Steam.

Don't these places keep their own source?

It's easy to lose track of important files when years go by with lots of employee turnover and migrating data across servers or to the cloud.

I'm a sysadmin and more than once I've had to shut down a file server just to find out what is still important when someone comes looking for it.

So I was listening to the WAN show, and Luke said that the DRM was stacked with booby traps that broke the game mechanically in a bunch of ways if the DRM was bypassed without also removing them. The crack did; their version didn't.