I have to agree but its on a different level I guess. Splash art for reworked champions should be REMADE as well. It really annoys me when I go to pick a skin on Trundle that his old Lil' Slugger and Junkyard splash art STILL aren't remade. Its been like 2.5 years. The traditional one I can let slide as a nostalgic nod to the old Trundle but part of me still thinks they should all be remade to actually represent the likeness of the skin they represent. (RIP Pink Shoe and Pan Hat).
I wish they would implement a system like the IP price reduction of the oldest 6300 champion becoming 4800 when a new champion come out. If they did it for skins, lore, art, perhaps maybe they would actually get done. There are multiple ways they could go about it.
The champion with the least amount of skins, gets a skin when the newest champion is released. If its a tie, the oldest champion gets a skin.
The champion with the most amount of time without a skin created for them gets a skin when the newest champion is released.
The same can be done with Lore I guess. I mean, they can kind of just do whatever they want with lore. Trundle was basically a Jesus troll before his rework. Renown for his regenerative power took the curse that burdened his tribe into his body alone, thus looking like a leper. (Sorry for all the Trundle, only lore I know.) They just scratched all of that story and made him a King. If they can do that, they can just redo lore as they see fit at any time, even if they do happen to pigeonhole themselves.
It could be because they are lazy, or perhaps they have bigger plans in the future like LAO said, but I'd venture to guess that some lore reworks just aren't high priority because its not going to make them any money in the long run. Sure its possible, but I think a lot of other things factor in at a much higher value than "Golly gee, this champions lore is darn tootin', better purchase some riot points so I can play this champion ASAP." Role, Abilities and Looks are probably about the only things 95% of people look at when buying a champion. Made up % but Id bet the % of people who care, and I mean REALLY CARE about lore, is probably a small number.