It's because they were 20 something hackers who wanted to tag, drink, party had playful repartee and zero dark past. But at the same time you had the option to 3D print assault rifles and bazookas and murderously rip into gangs, police, security guards killing everything in your path etc.
Playing non-lethal is the only thing that made sense for those characters. Going in guns blazing simply distracted from the game for me.
Listen, I am playing Assassin's Creed Odyssey and I kill the living #### out of everything that crosses my path (everything is permitted) so I don't have a problem with the violence aspect of it. But I do want to be entertained more than just mindlessly button mashing and that is where story comes into play. I just like my story telling to at least try and make sense and develop characters whose actions try and match their tone. I am not unique in that regard but I also know that I am probably not in the majority from that perspective either.
After all, it is a role playing game and, to be fair, I thought WD2 because a lot more fun once I realized what I found offputting about it and changed my play style accordingly. So good on them for making that an option.
The original Watch Dogs did have a protagonist, Aiden Pierce, with a military background and a deep trauma in his past. Taking down the guys who caused that trauma by any means necessary did make sense in that context. A kill run in WD2 was just weird.