I’d bet there is at least a small group of automotive mechanics that are interested in increasing diversity in their field.
A lot of industries that have issues attracting certain kinds of people don't have explicitly diversity goals as a part of their makeup. But that doesn't mean that people aren't trying to break into those industries and have a career there.
Keep in mind that the kind of work you do isn't just influenced by your hobbies and likes, but also by what is considered acceptable for a certain person based on gender/race/etc., stereotypes about kinds of work, and classism (among other things).
Then perhaps it is society that needs changing. But from the inside out. This patching from the outside in is never going to significantly affect the roots of the problem.
Web development is a profession, not (just) a hobby, and if women move away from it just due to the fact it's already a high ratio of males then it's a problem