It's a reaction to the Word-like screen-filling toolboxes of the late 90's. And while the toolbox not taking your entire screen would be a real improvement, what we got was a smaller set of larger buttons with plenty of negative space to make them look nice, taking approximately the same area as before, but with added clicks and discoverability problems.

Eventually the problem did go away because of larger monitors in a higher resolution. But well, nobody would ever think about going back into those ugly interfaces!

Oh, and count me as another previous Namecheap customer that isn't anymore mostly because of their interface. "Mostly" because I had one domain that needed DNSSEC when they didn't support it, and that's what started my migration, but what made me move everything was the interface.