Why not enable font lock by default?

[Stephen J. Turnbull]

Jason Spiro writes:

 > How many seconds is the delay for a 100KB or so source file?

Depends on the mode.  CC Mode seems to be the worst, with >5s being
common for a full fontification of a 100KB file.  This is unacceptable
especially when starting up with many files in your .emacs.desktop.