Don't even try the "embedded market" BS. Debian is incredibly bad for anything "small". How big is a pure "base" install again? A fuckload more than 99% of embedded devices have.
The entire logic (read: Debian Political BS) behind what arch's are supported is (a) popularity, and (b) having a pool of active maintainers. SPARC has neither of those. The entire backstory is over a year long and boiled down to some nut screwing up the gcc packaging -- changed only for SPARC, that broke only SPARC. (I smell a rat.) Ultimately, it probably needed to go. Just like for the PC -- where amd64 took multiple eons for the fools to finally support -- many eons have passed without a migration to a full 64bit distro. The build system still, to this day (22 years on), builds everything as 32bit. Yes, there's a 64bit kernel, there are 64bit libraries, and gcc can output a working full sparcv9 64bit executable, yet, they still spit out a 32bit userland.
(One would hope this lights a fire under the sparc64 ports project.)