> Isn't it better if let count is reactive by default?

> Well, no. The reality is that as applications grow in complexity, figuring out which values are reactive and which aren't can get tricky.

People keep re-learning that there's a certain amount of context that needs to be explicit, and you can't just imply everything. Just like when ruby and python made the mistake of getting rid of let/contst/var/etc and programmers said wait no that's a bad idea, now it just makes everyone's job harder, because neither the compiler nor the developer can figure out what context something belongs to.