They introduced the 6 ban system when there were 70 - 80 champions available. There's 131 champions at the moment.
6 bans per team are not enough, and this also makes competitive boring to watch, because as MSI taught us, there's only 20ish champions that somewhat viable. Thank god for Aphromoo's Sona because it was Poppy vs Ekko and Azir vs Ryze EVERY SINGLE TIME. Throw in **Lucian **and Ezreal, Nidalee and Graves and maybe Elise, and it's just boring to watch the same 20 champions played by every competitive team. Imagine if they had 8 or 10 bans to work with. Champion variety would go a lot higher.
Why some people refuse to see that 6 bans for 131 champions is way too low is really strange for me.
I wish I could up-vote you 100 times