If you assume the program is being passed through a JIT (a thing that is already common for interpreted code, and which also tries to guarantee that it doesn't change the resulting program's semantics), then one can think of jets as simply explicit hints built into a JIT regarding how to optimize particular known idioms well known in the corpus of programs the JIT was designed to work with.

This is exactly how GPU drivers get gradually more optimized for existing games: the driver's shader compiler actually has an ever-growing library of shader-source-code patterns, with hardware-vendor-optimized replacement sections.