Your supposition that wearing earbuds effectively reduces one's ability to hear what is needed to be heard on a motorcycle is a supposition based upon your opinion. The key word there is "effectively".
You put on a helmet every time you ride. You have reduced your ability to hear, but your effective ability to hear something like a car horn is really not reduced. You still hear it, but it's not quite as loud as without your helmet. This works out well because you're protecting your noggin and still can hear what you need to hear. So, you decide to wear a balaclava under your helmet because it keeps your head from sweating up the nice helmet liner. You have reduced your ability to hear, but not that much, really. That siren is not as ear-splitting now, but your head is quieter, arguably less moist, and you definitely can still hear it and with plenty of time to react. You read a thread about how hearing loss can be reduced by wearing earplugs, so you slip some Hearos in under your balaclava and your helmet. Wind and engine noise all but disappear, but amazingly enough, you can still hear the fire truck. Everything is working great. You have protected your head, kept it dry, and saved your hearing so your grandkids won't have to yell at you when you're old. Then, you watch MG's Equinox video and decide that "Into the Mystic" would a perfect accompaniment to your ride and you remove your Hearos and insert a good set of earbuds that help block all that wind and engine noise. You fill a little of that noise vacancy with Van Morrison and guess what? You can STILL hear the car horns, the sirens, your wife on the bike next to you at a stop light shouting that you ride too fast, and the sirens.
In the end, it's a matter of one's preference, I think. It's not crazy or dangerous to listen to music when you ride. It IS crazy and dangerous, however, to create an environment in your helmet where you cannot see or hear the things you need to see or hear. I think a person just needs to be aware that there is a point at which they simply cannot hear what they need to hear or are so distracted that they hear it, but don't react to it. If they stay well short of that line, they will be fine.
Oh, and never ride too fast if your wife is following you. Talk about needing ear protection!
