The Steam Hardware & Software Survey for June 2025 puts 32-bit Windows usage at somewhere under 0.05% of Steam users (which includes all versions of Windows except Windows 11, Windows 10 64-bit and Windows 7 64-bit).

The only usage of 32-bit libloot that I'm aware of is by the LOOT metadata validator. Its Windows builds aren't significantly used (they have 105 downloads vs 23652 downloads of the Linux builds), and it can easily be changed to produce 64-bit builds instead.

While there's not really any direct cost to producing 32-bit builds, and GitHub doesn't impose usage limits on GitHub Actions for public repos that use their runners, it does seem like a bit of a waste to run builds for a target that is barely used and will only be increasingly irrelevant in the future.