I wonder what kind of job opportunity it is that's both:

1) Worth following up on

2) Not worth the recruiter going to the trouble of finding your contact details through GitHub/your personal site.

It seems like the very lowest common denominator way of finding people, which would suggest that it would also have the lowest common denominator applicants, and the lowest common denominator jobs.

Much of this thread is 'What might you be missing out on' but I see developers who have chosen to own their own career identity and not federate it through a platform that every other attention seeking bozo is on doing just fine.