> a handful of HTML tables and forms

But that depends on the use case, doesn't it. Static sites may as well be huge, and now you need to send all of the surrounding html over, when only a small table or form would need updating. So I am not so sure about your point. The greater the complexity of the displayed page, the more sense it makes to use a SPA network-wise. (edit: mostly covered in sibling comments)

You have a point about compression though. I now wonder what the situation would look like if we had (had) native HTML imports, as that would greatly help with caching.