Tbf any variation of “one third of a pound” is a shit name, so all this proves is that they failed to market the product.

The real answer is likely that extra wide buns are not available from suppliers, and nowhere bakes their own bread these days. For the chains that have their own off-site bakeries and supply chains, the majority of consumers probably don’t want a much bigger burger, and those that do have big enough mouths to fit extra tall burgers, or buy 2 burgers which are easier to eat. I know if I’m extra hungry I’ll grab 2 cheeseburgers, but most of the time 1 plus the mandatory chips is enough childhood nostalgia junk for me. I wouldn’t care about a 50% wider cheeseburger.