For me it is confusing, that you can attack with off hand separately, when you got two weapon fighting, it feels like as if it could be done automatically.
It's done that way because attacking with the offhand weapon is a bonus action.
Could be, that the book says that, but still it is something that they could build in their own two weapon fighting system. It feels like, that I have to click too many times to attack, especially that most of them are miss with off hand.
Making them full attacks that don't cost a bonus action would tip gameplay towards dual-wielding as it's always better to reduce your opponent's action economy, and some classes have features that require bonus actions; that forces players to consider whether or not dual-wielding is worth it.
