I wonder if the "I'm feeling lucky" has stayed around because it's a good training heuristic for Google Home (and maybe other services?) even if very few people actually use it. I'm genuinely curious why they've kept it around.
1) It isn't very complicated -- it doesn't require a lot of code that is going to rot.
2) When it is used, it's cheaper rather than more expensive.
3) It only "clutters" a UI that isn't actually seen that often nowadays -- you have to actually go to google.com, rather than just typing in the browser bar -- and isn't particularly cluttered.