Because they don't really dissolve into the soil. The roots exude 'stuff' to dissolve the RD and make it available.
*I* only use Greensand and Azomite now @1cup of each/cf.
Wet
Maybe dissolve is inaccurate. Many organic growers create their soil mix and let it homogenize over a period of time to allow some of the nutrients to leach into the soil so that they will be available to the plant..
The basalt rock dust I got from buildasoil has rocks and dust in it.
The Azomite is powdered and looks like it would break down and allow some micronutrients to leach into the soil more easily than the others. Some growers complain it has toxins in it while the FDA generally recognizes it as safe (GRAS).
I haven't seen what Glacier dust looks like.
Greensand does not look like it would break down very easily but is great amendment for soil structure.
Azomite might be the best option since it is powdery and subcool used it with great success over many years.
Unfortunately, we don't know how long it takes any of the rock dust or greensand to break down in the soil. So, I just follow other's advice.