Getting an S // Mastery doesn't make sense
Got a bit lengthy, feel free to skip to the bottom sentence if you don't feel like reading. (:
I recently played a game in bot lane as Vayne. I'm no Gosu (I'm a bronze 3 player who doesn't play ranked. I play norms with friends) but I personally feel like i did really well. In my past game I went 24/10/8, almost doubling the kills of anyone in the game other than our Xerath mid. I understand that 10 deaths is a pretty high amount, but I warded properly, CS'd well for my elo, played laning phase really well, and all in all hard-carried my team. I did the 2nd most damage. Yet. I didn't get an S. I'm not upset at all, I understand that there are requirements that must be met to get an S and I must have failed to meet them, but I would like some insight on how to get an S. (at least as vayne)
As a second note, the game before this I played Jinx ADC and went 20/6/15 with roughly 250 cs, getting an S. But my problem with this is that I got an S, and earned a Token. A token? I have 230,000 mastery on Jinx. Why do I need a token to prove my mastery? Why not just make S's give you more mastery points past mastery 5. And even if I could stomach the idea of Tokens, what does blue essence have to do with my mastery of a champion. I'm not good at Jinx because I can break down a champion shard. The system all in all doesn't make much sense. Right now I have my 2 mastery tokens, but i'm lacking less than 100 blue essence. I get that it isn't a big deal, i'll get a bit of IP and break down a mystery champion token, but imagine doing this for EVERY champion you get to level 5, or 6. I can't waste my IP on that every time. I have 2 rune pages and not even half of the champions, I get that this system is catering a bit more towards the classic players who have all the champs, but it seems unnecessary and time-consuming to spend all of my IP on blue essence when runes are actually necessary to do well in mid to high-level play.
TL;DR: What do I need to do to get an S on Vayne, and why do Tokens and Blue Essence show how well iv'e mastered a champion?