I think this is simple: When playing with friends its near impossible to find someone on the Battlefield and its very, very VERY confusing to see a mate - there is no Marker over his head, no Name or something that shows (me) where he is on the battlefield without open the map. And even then its hard to see because players who play in the Solo-Mode are shown also with the same Marker on the Map with a different Number.
TL;TR:
Platoon Members/Friends in the Squad should have different/own Colors and should be highlighted.