It's path dependence. If you built a Sun-syle x86 server with a serial console and inserted a random Linux installer CD, the installer would probably only output VGA and thus it wouldn't work.
I would wager that almost no Linux installs are done by CD or displaying VGA anymore (maybe 0.01%).
Debian installer runs fine over serial, at least.
I would wager that almost no Linux installs are done by CD or displaying VGA anymore (maybe 0.01%).