I live in Austria where few cyclists wear helmets yet my girlfriend who works in the local hospital sees patients coming in with serious head injuries on a daily basis from biking accidents that could have easily been prevented by wearing a helmet. Since then we both wear our helmets religiously.
You don't even have to get hit by a car. An unfortunate collision with a texting pedestrian, some dog on a leash jumping in front of you or another cyclist could be enough to smack your melon on the asphalt.
Just because you hear Europeans aren't wearing helmets doesn't mean it's the model to follow. I see wearing a helmet the same as wearing a seatbelt. Sure I never needed it since I never had an accident and it feels slightly uncomfortable but I know it could save my life.
It's up to you how much you value your head.
I highly doubt ebikes have a 50% share in Belgium. Do you have any references on that claim? Last year I visited Belgium's 4 major cities and almost every cyclist I saw was on some old half broken bicycle.