Parmandur
Book-Friend
Having certain Species options isn't necessary to use Planescape. Folks who have MotM have an array of options thst can fit in Planescape, the Forgotten Realms, Spelljammer, Greyhawk, or wherever. Modrons are pretty Planescape specific, but you could have an all-Human party in a Planescape game. MotM is for people who want thst wide array of options, and it's not necessary to reprint incidental options from it.Not everyone else has that, alot of folks don't, perhaps it would be better to think of others then yourself. Like I have Aasimar, but I don't begrudge their stat block or a variant version being in the book given Aasimar lore is going to be in it anyways, and a race stat block is a tiny amount of space. Requiring something other then the PHB/SRD and Planescape to use Planescape is not right.