My experience at Google has been that TLs were generally strong engineers who were doing that kind of mentorship and product leadership, so to the degree that it's a "promotion" (same money, more responsibility isn't a promo in my book) it does seem to go to those who are doing it.

Now TLM (Tech Lead + Manager), however......there's a role that's set up for failure. Be a manager but be judged entirely on your technical contributions.