It's possible, but there are always competing goals - speed, security, reliability, features, memory usage. When capacity on one is growing quickly (and cheaply), it's not surprising it doesn't get the same priority as some of the others. In particular, I'm not sure how many extra users you'd get by reducing memory footprint versus adding features.

But this has been discussed ad nauseam, and it's unproductive to keep complaining about it. The fact should be obvious, at least by now, that sandboxing uses more resources. If you're fine with that, great! If not, do something to fix it or use a different browser.

This sounds like it was possibly some time ago. If so, don't discount the effect of having less resource-intensive sites too.