ctags doesn't understand -e option (no exuberant tags option)

etags is short for "Emacs tags", not "exuberant ctags". It sounds like you have Emacs' etags command installed, not exuberant-ctags'.

It turns out that my system has basic ctags installed, but not exuberant-ctags. so even though some etags command existed, exuberant-ctags is still different in some way or another.

sudo apt-get install ctags fixed the problem

sudo apt-get install exuberant-ctags 

solved the problem for me. I was running Debian Jessie on an ARM development board, cubietruck.