There were multiple sizes of tubes, so the unit had to have a bunch of different sockets on top to accommodate anything someone might have. That forced the top of the unit to be the size it was, to fit all those sockets. Then, the pedestal held the replacement tubes, so that also had to be big enough for drawers full of boxes.

It was common to bring in multiple tubes to test, since you wouldn't know which of the tubes in your TV or high-fi set was the bad one. You'd test several, and buy a replacement for the bad one.

I remember doing it with my Dad. He'd pull out all the tubes, put them in a paper bag, banging against each other, which made me wince, even as a kid. Then we'd go to the store, and he'd test them out, and buy replacements for the ones that didn't work. Then he'd replace them all, and sometimes the TV would actually work again. Sometimes.

Maybe there are just that many non-standardized socket types