My guess would be that it's supposed to be an easier UI for people who want to casually book flights (as opposed to the FT community). A lot of the old features of GF were kind of buried in menus. Good for us because we knew exactly where the menus were but probably bad for their usage metrics.
The main thing I hate is how laggy the UI is (although it's gotten better since the early days) and random bugs that pop up (my search got "stuck" and I had to refresh the page/start a new search once or twice).

Anyways, I'll ask and see if I can find the "real" answer.