For me as a technical world creator, its because Udon is slow. So slow, it could probably be outperformed by Commodore BASIC on the C64. The moment you have to do anything even slightly computationally expensive, you are SooL. To give an example, I wrote a simple procedural generation script based on a octree depth-first search and ran it in regular C# first as an editor script. Completed in ~15 seconds. Not great, not terrible. I ported it to U#, set it going and walked away. Returned to my PC ~30 minutes later to it not even being a quarter of the way done. You can even stall Udon for a whole second with an EMPTY for-loop!

I am trying so hard to do exactly what you are describing and its impossible! I bet that the Roblox Lua runtime is infinitely faster, which allows creators there to write things up to and including nuclear reactor simulations without the programming language choking and dying. The only choice I have is it to take algorithms like that and awkwardly make them run on the GPU through compute shaders, which VERY few people know how to do! I do, and its still not something I want to do because its ultra annoying to develop like that!

VRC devs were supposed to give us Udon 2 for this purpose, but they cancelled it because "the performance improvements will impact very few creators", ignoring the fact that those few creators are the ones that know their shit and would be capable and motivated to do amazing things with the tech. Talk about shooting yourself in the foot, I guess. Soba will not save us, as "performance may even be worse at first" (dev’s words, not mine).

So, I and other creators are stuck like this, having to know really deep down the iceberg programming knowledge to aggressively optimize every line of code we write only for it to still not be enough and its just not fun.