What do you propose nginx does? Should they embed rust, go, c, visual basic, turbo pascal, nim, and 37 other scripting runtime? Should they pick 3 to support?
How many of these have embedded scripting systems? How different will they be? How many offer lightweight nano-processes? How many are secure sandboxes? How many support arm, RISC-V, or the next architecture?
Having a common platform here makes so much sense to me. Enabling a variety of things, safely, quickly, & with well defined patterns, seems intuitively advantageous, frees us from having to tangle with a variety of minor subdivisions that fix software onto narrower paths.