There are also just fashions with such things--I've seen a lot of cycles between the early 2000s and today--as well as a lot of variation among companies and between individual roles at companies. In some cases, a senior developer is sort of the public face for a new technology they've been involved with and promotong.

It's perfectly reasonable for someone not interested in doing this sort of thing to push back--they won't do a good job anyway if they're being pushed to do it. Others get a lot of recognition by writing and speaking. I'm not even sure the hiring pipeline is that big a part of the rationale.