Just from what I have seen and heard because I have been watching the subject for years.
They cost quite a bit.
They very often never actually run right.
They often don’t last a long time. (Failure rate)
Ahem. A/C.
I can't justify a fuel injection system to myself, even though I do want to try a coil near plug setup. I know carbs + coils near plugs is somewhat Frankenstein.