I have a few old PCs (towers) here which don't support amd64 mostly Pentium 4-based.

They all still have DVD reader drives and are nice for ripping CDs. Despite the fact that the drives are nearing 20 years of age (machines are from ~2005) they still perform better than most “new” external drives. Of course one could also move the drives to a newer machine but many of them use the IDE connector which is not commonly found on modern systems. Also, modern cases typically don't account for (multiple) 5.25" drives.

The other use case is to flash microcontrollers. When fiddeling around with electronics there is always a risk of a short circuit or other error that could in worst case kill the attached PC's mainboard. I feel much safer attaching my self-built electronics to an old machine than to my amd64 workstation.

Due to their age, I think the old machines may not live much longer -- I fear not even 10 more years, some of my old 32-bit laptops have already failed. Hence even for me it does not make sense to try keeping up the software support. Maybe I switch them to a BSD or other Linux distribution if they live long enough but for now the machines run OK with Debian Bookworm (newly oldstable), too.