I'm asking mostly out of curiosity, but I had a use case that I would like to completely avoid a build step. At work we have a very old web interface, that when I attempt to sell the idea of any major improvement the answer is "this is end of life, we are rewriting it". But the rewrite will take a long time, and it is easier to make gradual improvements without introducing new tooling. This one is from the 90s, there the JS is in a folder and is shipped as is.