Most of the 'uploads' supported on SE are embeds organic to a post. Images are often useful in questions, YouTube embeds are useful on sites about media and so on. There's an exhaustive, and hopefully complete list here.
Blender has a file upload someone in the community setup, because their site needs it.
All those 'enrich' a post with appropriate content, rather than acting as a store of things that wouldn't fit into a post. In the Stack Overflow version of how to ask a good question (which goes into more depth than ours) it says
Not all questions benefit from including code, but if your problem is with code you've written, you should include some. But don't just copy in your entire program! Not only is this likely to get you in trouble if you're posting your employer's code, it likely includes a lot of irrelevant details that readers will need to ignore when trying to reproduce the problem. Here are some guidelines:
Include just enough code to allow others to reproduce the problem.
...
DO NOT post images of code, data, error messages, etc.—copy or type the text into the question. Please reserve the use of images for diagrams or demonstrating rendering bugs, things that are impossible to describe accurately via text.
The proposal as written encourages users to dump entire environments, voluminous logs and other artifacts as a whole, rather than spending the effort to sift through it. It also moves information needed to answer a question away from the question, which practically means a lot of users are going to be frustrated because question quality can suffer, or someone dumped everything they had and no one reads it to answer.
Generally I don't think most random strangers are going to download your entire environment and troubleshoot the whole thing for you.
There's also the risk of secrets leaking when you do something like upload your entire environment. Private keys, passwords and so on. Least in a actual post we can redact that information; it’s not as easy with a file host.
