We do? It's -a for short options, --foo for long options, and /too for DOS/Windows. Some commands break the standard and use -long, but that's their own bug.
same for -help / --help. And there are the rogue commands that use -? and --help for the same...
Perhaps I don't understand what you are talking about. One hyphen for single-character combinable flags, and two hyphens for multi-character flags.