Rocket Jumping emerged entirely by accident in the days of Quake, by players, not the company. Educate thyself.
Maybe, but it was an exploit in the days of Quake and Team Fortress Classic (and rocket and grenade jumps really broke certain default maps in TFC, to the point that there's almost no point in flag running if you aren't a medic on some of them), while they clearly started deliberately designing the maps with rocket jumping in mind in TF2, basically making it a class feature (while taking the grenades away). Overwatch followed this example.