Macros can accept any text command. There would be a massive overload of icons for all the slash commands that deal with settings, chat, social/search functions, target placeholders (<t>, <pet>, etc.)... Just the new inventory sort commands and /hotbar seem like they'd be a nightmare to represent graphically, and they'd have to do all this for every new command they added, too.

On the /wait subject, they've stated that it's intentional to not have it activate skills with perfect timing. It's a trade-off for the ease of use.