/summon Doesn't Have an Option to Summon Onto a Player

If you type /summon or /setblock, it only gives an option to summon/setblock at coordinates, when I feel it should be able to spawn things at a player. "/summon <EntityName> [x] [y] [z] [dataTag]" should be "/summon <EntityName> [x] [y] [z], <player> [dataTag]".