A full page load is very disruptive to application flow, and being able to have new data appear without incurring that penalty is great
On many examples I don't see any real disruption to application flow with just using normal links, though there are more full-fledged webapps (like gmail) where I would agree. Playing around with old v. new Twitter, the old one actually has considerably faster navigation performance, at least on my setup (and I'm using a recent Chrome on a recent Macbook Pro). Sure, some HTML header/footer stuff is being retransmitted, but it's not very big.
On many examples I don't see any real disruption to application flow with just using normal links, though there are more full-fledged webapps (like gmail) where I would agree. Playing around with old v. new Twitter, the old one actually has considerably faster navigation performance, at least on my setup (and I'm using a recent Chrome on a recent Macbook Pro). Sure, some HTML header/footer stuff is being retransmitted, but it's not very big.