Making a language is fun, and builds your skills. I'd rather work with a person who has made a bad language than someone who has never made one.
Don't make fun of people for making languages.
Don't make fun of people for making languages.
Also Obligatory:
http://james-iry.blogspot.com/2009/05/brief-incomplete-and-m...
Some day, that may become true. But the safe-money bet is on "no" for the vast majority of languages one will encounter in academia and industry. Most will fail to catch on, a few might be remembered, and the ones that succeed will do so because of forces unrelated to the zen of their design as much as the new ideas (or old ideas done right) they bring to the table.
(They share that in common with startup companies ;) ).