Companies write job adverts using that language for one of two reasons - either because they think it's flattering and want to get developers who will fit in to a culture where they already use that language, or because they don't understand the language and think that will attract the best people.

The first type of company is a great place to learn new things if you're quite junior. The second is a good place to demonstrate your ability to hack solutions together fast if you're mid-level.

If you're more senior then you should probably avoid all of those sorts of companies because neither will want to do things in anything resembling a sane way.