Paladins need to actually be Paladins.

[Airal]

It's true that Paladin in its origin is basically just a fancy word for Knight, but within the series they've rarely deviated from a structure so wildly. They literally have no access to combat ready magics whereas every other iteration of the Paladin job/class has used it as an integral part of their kit that distinguished them from just being a dude in armor with a sword. The only thing that really stands out to define Paladin in FFXIV is Hallowed Ground, which is calling back to the generally accepted faith mechanic of the standard fantasy Paladin.

They've proven they can do Summoner several different ways while keeping the core mechanics (the summons) in tact. I see no reason that Paladin for this game in particular had to be so different.