99% of ARM usage is done in little endian. all android & ios phones, all embedded boards that ship with linux, etc. are always configured in little endian.
Okay, assuming you're right, how much overhead is it to consider endianness? I've never had issues with it, unless I'm implementing something fully from scratch, and that's rare in a production environment.
People that deign network protocols love love big endian.
Which means on the software side you then have to swap everything from big endian to little endian. And you need to do that at the first opportunity so their big endian crap doesn't get loose in the rest of the code.