Can someone tell me why blue essence is required for mastery banners?

TL:DR/BLUF - I think Riot should revisit the blue essence requirement for mastery banners

Okay so I put a fair amount of thought into this, and I still feel I need someone to explain what I'm missong. I play, I get chests from time to time, and I practice champions a lot. Some more than others, and one more than all. That one I have Level 7 on because I spent the blue essence required (at the cost of loot that I probably should have saved or used). I also have level 6 on a few champs. I also have level 6 and 7 tokens for champs, in some cases enough to turn in, but I have no blue essence...

So here's what I don't get. Why does there have to be a blue essence cost? I get earning tokens for exemplary games with a given champion based on metrics that you need to excel in with that champion, and honestly I might make it a little more stringent or have the token numbers be higher. But I don't get why you have to give up the hard earned loot for another champion to turn it into essence that you then use for the banner. It makes it seem to me like the loot system is a decision tree - skins and such, or mastery banners. Now, I get that I could play each champion until I earn a chest with them, and then cycle through them all and maybe even repeat whenever the chest resets for a given champion, but it took me a pretty long time to get to where I was consistently earning A range games with a given champion, let alone S range games to get a chest.

That means that in order to get anything worthwhile out of the loot system, I have to have excellent games with a large number of champions and therefore a pretty darn good player. I've been playing since something like S2 or thereabouts, and I am pretty good with... a couple champs. I'm mediocre at a few more, and I'm thoroughly Bronze even though I've finished the past couple seasons in Silver. I would like to think I am better than I am, but I know that I'm not and I have no delusions about it. Point is, I doubt I'll be racking up chests any time soon or likely ever, and it took me years to get to this point. So what am I missing here?

Full disclosure, I'm what many of you would consider old. I will never have the reaction time of many of you, and I know that it will only get worse no matter how smart I may become in terms of the theory of the game. So where someone may say "oh, I picked up the game and by the time I hit level 30 and jumped into ranked, I was Master tier, it's not that hard" please remember that not everyone is a teenager at the peak of their gaming career. It's okay to be a casual, I swear.