There's a lot of different kinds of "using". "Memory pressure" includes some kinds of caching (ie running idle daemons when they could get killed) and not others (file caching). And there are also memory pressure warnings (telling processes to try to use less memory), so there's a lot of feedback mechanisms.

I don't suggest sitting and looking at Activity Monitor all day. I think that is a weird thing to do as a user. If you would like to do that in an office in Cupertino or San Diego instead then you can probably figure out where to apply.