Why materialists are predominantly materialists

[bennyboy]

First of all, I don't "believe in" idealism.  I'm agnostic about the nature of reality, but I consider a kind of experiential idealism a better default position than a material monism.  This is because there's a 100% chance that all knowledge is known only by a subjective agent, and an unknown chance that all subjective agency is dependent on a material substrate.  100% > not sure, any day of the week.

More word games.  Your odds don't make any sense.  Both "all knowledge is known only by a subjective agent" and "subjective agency is dependent on a material substrate" may both be true at the same time.

Yes, they may.

 And  "all knowledge is known only by a subjective agent" doesn't lead to Idealism.

No, it doesn't, at least not necessarily.

However, I'd say a few things about that:
1) Since there's no way to know where experiences come from, or if they come from anything, the default position should start with experience-- not something else.
2) Whatever might be "out there," for sure we experience it only as ideas. The human existence is for sure idealistic. And in a sense, it doesn't really matter if we're in a physical monist reality, or a substance dualism, or the Mind of God or the Matrix: it is our constant dance with experiences and ideas that define us, and in which we live and breathe and write forum posts.
3) The material world view is subsumed by idealism. All math, all physical science, is anyway represented as ideas by us. However, many things, but especially qualia, are not well represented by math and the physical sciences.
4) The duality of photons, in which a single entity cannot be expressed unambiguously in space and time, is perfectly workable as an idea-- but not as a material "thing."

I declare as agnostic-- very simply, I don't know for sure what lies behind my experiences. However, idealism has a broader scope than materialism, and until proof is furnished that the scope must be limited, there's no advantage in being a materialist, and there's a very real disadvantage-- that one's view of what "material" means may limit avenues of inquiry, in science and otherwise, thereby serving as an obstacle to the improvement of our understanding of reality.