Makes sense for inheriting the chain and in essence still being Bitcoin, as Bitcoin Cash is trying to do. But to create simple altcoins, it might also make sense just as a way of increasing adoption if it actually is useful. If it's not, then obviously not.
Also, if the coin is different enough from whatever community you are airdropping to it might be a problem that there is no significant social overlap and interest. Then the point of airdropping it goes away completely.