Hell their main site is a mix of various styles of ui changes from over the years. It's really inconsistent and sometimes confusing. Example being search filters. You can check the prime button but changing another filter may remove it.
What do you think the reason is? My thought is, not many people complain loudly so why invest the resources in an overhaul. If it ain't _totally_ broke why rock the boat kinda thing.
That or the engineers build the frontend ;-)