Well it is my impression people disallow color because they don't know about the /strip +c command
Plus I didn't even mention /ignore +k nick which ignores colorcodes from that person but lets the rest through.
Also, IRC is a social gathering, so rules of politeness apply and it would be more polite to disable color on your client rather than act like a nazi to every stranger, but perhaps that's my weird old world view of politeness eh..