Played that way in the old days, and still play that way now. And those PCs are perfectly fine. I don't have to play harder, or they don't get killed easier. Probably a lot comes down to style of play. Combat is only about 1/3rd of our gaming time, so for the most part, that extra +1 or +2 bonus isn't even a factor. We also don't track how every other player is doing, so no one notices that +1 difference when it does come into play, and no one gets jealous or upset if another PC has a higher stat somewhere. We view the party as a team, as opposed to a competition between PC stats. There are nearly infinite ways to interact in the game. Typically, it's the most creative PLAYER, and not the most optimized CHARACTER that has the biggest influence in how the game goes. First and foremost, it's a social interaction for people to have fun together.
As to your point, some of my most memorable PCs were suboptimal. No one remembers that PC that always succeeded and always did well because it wasn't challenging. We remember when the PC who has challenges overcame the challenge (either through luck, or creative play) to win the day. Flaws and weaknesses are what accentuates the strengths and heroic actions. Like one of my oldest PCs I converted to 5e from 1e, my fighter merdock. Back in 1e, I didn't get the roll to be a paladin, but that didn't stop me from putting my highest stat in CHA and role playing him like a paladin. Did he do the most damage? No, not if you spent the time to analyze it, but it wasn't really noticeable in game. But he was very good at intimidation and inspiration, which often overcame many challenges