Comment by Arainach

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.