[luckylion]

Regarding allowlisting the other major crawlers: I've never seen any significant amount of traffic coming from anything but Google or Bing. There's the occasional click from one of the resellers (ecosia, brave search, duckduckgo etc), but that's about it. Yahoo? haven't seen them in ages, except in Japan. Baidu or Yandex? might be relevant if you're in their primary markets, but I've never seen them. Huawei's Petal Search? Apple Search? Nothing. Ahrefs & friends? No need to crawl _my_ website, even if I wanted to use them for competitor analysis.

So practically, there's very little value in allowing those. I usually don't bother blocking them, but if my content wasn't easy to cache, I probably would.