Mainframe OSes including mainframe Linux are Big Endian. Maybe mainframe Linux could switch but thus far it has not, it seems unlikely the other mainframe OSes would want to. AIX is also Big Endian and seems unlikely to switch and will be supported until at least 2040.

Personally, I find big endian a lot more natural when doing hardware development. I understand there are people who think the opposite. As far as performance it is negligible.. network order is Big, PCIe is little so you are usually eating some conversion on either platform.

I also really don't understand why people thought it was such a hard concept as to largely force Linux (PPC, arm, mips) toward little.