Phillips head screws have the advantage of being power driven, something which you can't easily do with slotted screws. Phillips headed screws were one of the earliest designed for power driving, there were some others but the Phillips was the most popular. In more recent times others have been adopted, Allen and Torx have the advantages that they will stay on a driving tool without any fancy clips or holders but Phillips are still the most common. The worst problem with Phillips is people using the wrong sized driver which will quickly strip the screw head. The main drawback of Phillips heads is that they make removing screws more difficult because you need a lot of downward pressure to keep the driver in the screw head which conflicts with the action of the screw wanting to rise up against the force while being removed.
Goldwing 1500, Silverwing 600, Schwinn 49