In the Netherlands they banned wearing earplugs/headphones on bicycles for this reason (as well as using your device). Whether that's enforced / enforceable is another matter though.

On a motorcycle you need hearing protection due to wind noise, but good plugs will filter out the louder noises, not so much important ones.

On a pedal bike, it's very important because you are most likely to be hit by cars from behind. Motorcycles move much faster, and most riders wear helmets as well, already impacting hearing. The road noise and wind is very loud, try rolling down the window in a car on the freeway and imagine that on .your whole body.

As a cyclist, I find sound such a poor signal I'd consider it optional. Too many threats are silent and sound is too late, misleadingly bounces of other surfaces and generally poorly correlated with significance.

Safe cycling is all about vision. If you can't see it's safe, it's not. It isn't simply seeing imminent threats but predicting them e.g. identifying drivers that aren't paying attention and where a car could suddenly emerge like blind turnings, car doors, pedestrians and such, and countering with appropriate caution / road position.

If you find noise useful, IMHO it means you aren't sufficiently aware of your environment.

There is practically nothing to hear that matters for your safety on a motorcycle at highway speeds. An ambulance you will hear even with headphones.

Ear plugs are recommended while riding a motorcycle.