Why is this still a thing?

No idea.

For bot lane, I'd assume, as a supp main, a good adc is hard to come by while trying to climb. Something's can only be done with a real partner

yeahhhhhhhhhhhhhhhhhhhhhhh, GO JON OLIVER

Yes, but bot lane typically feeds the most as they are forced to work together throughout the game, with no solo laning phase. As such it is more important to have the opportunity for proper synergy than just getting a lucky match.

So what? I always queue up with a friend of mine. We are always friendly and do well together, not sure about other duos though.

meh, it's fine, If two people are better at working together, then I don't think it is as big a deal, as compared a full team going LCS on your ass. Lol is a team game, after all. Even though Flex Queue has its own problems (boosting), it's unlikely that Riot believes that having a duo partner is a bad idea. I'm pretty sure they developed flex/dynamic queue based on consistent positive reception to duo queue over 5 years. Apparently, actual teamwork is not the point of the game, instead it's the ability to solo carry a game that makes ranked fun to most people. Anything that gets in the way of that either has to be nerfed or removed right? I feel like many people perform better when they know someone has their back; a feeling that no one EVER communicates in ranked. It's always a pretty negative, 'you died once, I report you' or constant chat spam (which can be muted), essentially gives a person the confidence to play better. While it may hurt people who'd like league to only be solo, that's not the point of a 5v5 map. The most common scenario in solo ideal is everyone is god at their champion and happen to work together somehow. Duo makes it a bit easier to pull off some really fun combos and plays that you wouldn't be able to do with random people.