I get where you're coming from, I do.
There are plenty of winnable games that people give up on. Lots of times, an early surrender vote is jumping the gun. I've had people try to surrender at 17 minutes, one time, and then never again, because something happens to make it clear that, hey, we're very much not out of this fight. Even if we're legitimately on the back foot, I've seen failed surrenders for games that we eventually won. So I can definitely see your point about all this. And maybe it would be worth dropping the option to surrender, since most games that are lost by the time you can surrender aren't gonna last much longer.
Buuuut on the other hand, I don't always surrender because the game is lost.
A few times, people have had emergencies pop up in the real world and have to go. So I surrender when they ask me to, because the real world matters more.
A few times, I've surrendered because even if the game is winnable, it's not FUN. I never do this in ranked, because if you queue for ranked, you're committing to seeing things through to the end, and I don't mess with four other people just because I'm not enjoying things. But if it's normals and the enemy team is ahead and I can already tell that I'm not going to enjoy playing through even if I win, I'll hit 'yes' if someone else surrenders.
But the most common reason for me surrendering isn't actually because I think we can't win, or because I'm not having fun, or because of emergencies.
It's because I do not want to play with the asshat that I got put into the game with.
Again, I don't do that during ranked, but there are players I run into that just enrage me. A mid laner who feeds three kills to their opponent and then has the gall to sit there and complain if the jungler gets killed trying to bring back control of the lane. An ADC who thinks League is a spectator sport when he's Twitch and I'm Sion and I just held the entire enemy team down for 5 seconds. A jungler who pings that they're heading top and at the last second wanders off into their own jungle right as I set up the gank for them.
People like that. I surrender because I have better things to do than play with a handicap.