That's part of the answer to the OP's question. I thought that ext2 might have caught on, but I guess vendors were scared off by the GPL and (later, when BSD licensed implementations became available) the lack of support on Windows.
If you're being practical, the FUSE driver is just a PPA away on Ubuntu and works fine in my experience. I've switched over all my external media to exFAT, including my external hard drive with virtual BD-ROM functionality.
https://en.wikipedia.org/wiki/ExFAT#Restrictive_licensing_an...
That's part of the answer to the OP's question. I thought that ext2 might have caught on, but I guess vendors were scared off by the GPL and (later, when BSD licensed implementations became available) the lack of support on Windows.