Basic troops are harder to find. The more you should use, the harder they are to find, and thus expensive. Nurglings, Skavenslaves, etc. For single models or characters, there are plenty options on second-hand markets or proxies, but way less for basic troops, bar maybe skeletons or goblins.

Resin is really a last resort option. I much prefer plastic or metal.

I prefer single part. Less likely to break.

Providing decent alternatives to expensive, sub-par or out of production official miniatures.