The team at Unreal have clearly spent more time thinking about this than you have. The Generate Overlap flag is used for any collision profile, for example, your player character is set to block all, but you want him to generate collision events so you flip the flag on. The crate is also block all, but you don’t want it to generate collision response, so you turn it off.
Reason why its off by default is for performance. And you’re example is very extreme, I don’t think I’ve ever needed one trigger to detect literally every game object, which would mean having every object generating overlap events. To me, that sounds more of a design issue at that point.
Keep in mind, your solution doesn’t actually change the reality of the performance issues that would come with everything being generate overlap events, you would just remove the ability for a designer to create a static mesh that won’t trigger triggers.
TLDR Unreal doesn’t make the assumption because it can’t make the assumption. There are many profiles, plus custom profiles where you can overlap and block at random, so there’s no way for it to know you want it to generate overlap events. So it makes a lot of sense, I don’t understand why you thought this warranted a very long and formal post…