> Because it's faster. In my experience sites with these kinds of navigation are typically extremely slow with initial page loads taking anywhere from a couple

> Because it's faster. In my experience sites with these kinds of navigation are typically extremely slow with initial page loads taking anywhere from a couple seconds (bad) to 10-20-30 seconds, sometimes even a minute (on a 100 MBit/s connection) and subsequent navigations are often slow as well. It can be hypothetically faster, because you can theoretically get away with less data transfers and less client work, but in practice the exact opposites materialize.