So how is banning and picking first beneficial in ranked?

Being first ban means that if you pick someone they were going to ban, they don't have to ban that champion and you effectively give them an EXTRA ban. Being first pick isn't exactly beneficial either except for the few times you actually need to pick a certain champion before they do. Sure, it might work in LCS where the team has every champion, they can switch freely, and they already know who their opponents are. They can take away champions from their team with the first pick. Not in ranked though. In ranked you have almost no idea if they are going to pick a certain champion or not. If the champion was good enough to warrant that kind of thing, it was most likely already banned. There can be 2 situations I can think of. You or the other team has banned all of the very obvious counter to a well known champion, then you should probably first pick them. (Ex. banned draven, caitlyn, twitch, all obvious counters to vayne) I've seen this often in low elo lol. You purposefully didn't ban a champion that is considered op that has a high pick rate.

But other than this, having first pick just leaves whatever pick was first open to being countered. This is especially prevalent in bronze, silver, maybe gold where lots of people haven't fully learned to play a champion. Solo players probably wouldn't switch and I've seen adc's that pick vayne or kogmaw first because they couldn't switch and got destroyed by their counters.

Am I missing something?