Originally Posted by DesmoDog

Because the vast majority of them are not ridden on or near a beach.

Same could probably be said for "mountain bikes", but that term was used to describe a new style of bike. The term cruiser has been around forever. Beach bike? I was a bike shop employee for ten years in the 70s & 80s and don't recall ever hearing the term back then.

But yeah, I'd also agree with why does it matter?