There are companies that use Intel Mac Minis as rack mounted servers. My guess is they are keeping them around for specific use cases like these. I’m sure at some point they’ll switch over but are giving companies time to prepare.
I forgot the 2018 Mac mini went back as far as macOS Mojave (i.e., can still run (some) 32-bit apps).Servers.
Also, Rosetta 2 has done so well for me. Even an app such as Air Video Server HD (circa 2012-2014) still functions fine in Big Sur on M1.