Why is Minecraft in high demand?

Because tonnes of 8 year olds have nothing to do but play it instead of playing with their legos.

Because that's what people want; blocky games with endless creativity and simple graphic. Unless, of course, you download texture packs.

Supply and Demand.

Some people want it, some don't.

But hey, it looks like it's still in high demand, so the public must still want it!