You may find this helpful. I think part of designing a good game is making choices actually matter; if the reserve list policy disappeared tomorrow, and they started doing functional reprints of ABUR duals, we'd see an even
more unhealthy Standard than we do currently. For all the noise made on these forums about offering better fixing in a
cube, there is a utility in conditioning fixing in different ways, and this counts especially so for constructed formats. Players will do whatever you incentivize, even if it's not fun; everyone playing 4-5c decks might sound fun to some people, but I don't think it's particularly fun or healthy for the game in the long-term, personally.
Working from a base assumption that enabling easy 4c/5c deck assembly works
against the health of the game, we can quickly conclude that Check Lands and Reveal Lands (the SoI lands) would be pretty stupid with basic land types, as they'd then feed each other, reducing the cost of using them significantly.
Similarly, Temples are awfully strong as they are; Scry 1 is a powerful addition to a land, and I don't think it needs to be pushed further with the ability to fetch/landcycle for it. Scry is a great mechanic that makes for good games, but tacking it onto a land that fixes is already juicy enough, again, assuming our goal is a diverse format.
As for Fast Lands, since they ETB tapped when you have more than 2 lands out, the land typing doesn't even really seem very useful? I guess they help offer an even
better early game curve-out with fetches, but imho shocklands offer this benefit at a much fairer rate of 1
Shock to the face.
Painlands are really old and were originally printed as a powered-down take of ABUR duals, which they felt were unhealthy for the game. I guess one could ask why they
didn't then, but they're honestly so old... Even if they wanted to print new ones that were fetchable, they'd probably exist just under (or maybe right on par with) the power level of Shocklands, so I guess that's a
reasonable request, but not one I think is super necessary.
The simplest explanation, of course, is that these have basic land types because they want to sell packs.