In situations where it is inconvenient / impossible to manage / rely a bunch of library files, dropping a static compiled tor in place is handy. Similarly, it should be possible to completely configure and run tor in that one static binary and in ram... no other files at all (torrc, geoip, .tor state dir, etc)... depending on your config.
It may be necessary to compile in a basic torrc just to get tor going, before you can spawn a control port. Other torrc/commandline options may not as of today be available via the control port... so they would need compiled in and just run './tor' .
In some unique situations you may not even be able to spawn/access the control port. So ability compiling in HS keys etc would be useful there.
There may already be some tickets for these things.