Why aren't cards with the older wedge ordering (Lightning Angel, Kaalia of the Vast, etc) updated to have the modern order of mana symbols when they are reprinted?

They would be if the frame was updated. Mystery Booster are straight pick-ups.

I was just reading the Dominaria Oracle Changes, and there is mention of ordering colors now that Jeskai (for example) makes the distinction of it being URW versus RWU on Lightning Angel. Does this mean that there is not any plans to try and differentiate a cards color pie identities? Is this just something a few of us were interested in and holds no actual value to the gameplay? I like to often think about the difference between a character that is WUR instead of RWU or UWR, etc.

We want all mana costs to be in the same color order manawise.

Sorry if this as been addressed before. Some multicolored cards follow the order of WUBRG in their mana cost. WUBRG cards cost WUBRG, UB cards are UB, etc. But other cards like WG cards cost GW and WR cards cost RW. Why is that?

Here is Del Laugel, Magic’s lead editor answering this question in a 2002 Ask Wizards question: Q: "Why do mana symbols seem out of order on various gold cards? Some cards requiring green, white, and blue mana, like Treva’s Charm (), have it in that order. Some cards, like Phelddagrif(), go white, blue, and then green. Rubinia Soulsinger () goes blue, white, green. Shouldn’t there be more organization?“
– Cid Silhouette, Boston, MA A: From Del Laugel, Magic technical editor:
"As you’ve noticed, three different systems have been used in the past to order mana symbols on cards. One system always put the colors in the order white-blue-black-red-green, and that ordering was used for Ice Age, Tempest, and Chronicles. Another goes clockwise around the "pentagon of colors." Mirage block used that ordering, and we’ve been following it consistently since Stronghold. And then there’s the Legends system, which involved throwing mana symbols into a hat and then pulling them out at random. "Our current (and final!) system for ordering mana symbols is pretty simple. If you look at the back of a Magic card, you’ll see the pentagon of colors. Going clockwise, the colors are white, blue, black, red, green, white, blue, black … . To order a pair of mana symbols, find them in that list, and then put them in whichever order puts the fewest colors between them. For example, white/red has two colors in the middle (blue and black), but red/white has only one (green). That’s why Goblin Legionnaire’s mana cost is . "Then came the Apocalypse 'wedge’ cards. Our system breaks down when you’re trying to order two friendly colors and their common enemy, and Apocalypse has five rares with mana costs that fall into that category. For Lightning Angel’s mana cost,  and  are equally valid options. In the end, I decided to put the enemy color pair first. ”(Yes, I know that the Apocalypse split cards all violate the color order. It was decided that those five cards would be easier to name that way.)“