Battery / Electrical Question from a Newbie

[WowWhoaWeeWa]

Ok, this might have asked before but I didn't see any recent posts about this. Can we talk about batteries for a moment? My bike is going to be used almost on a daily basis. I was told even though it's going to be used often, I still need a battery maintainer because, unlike a car, a motorcycle engine does not have an alternator keep the battery charged. O_o That seems odd to me. My only experience with "alternator free" motors consist of lawn mover engines. I recall they maintained the battery just fine.

Are motorcycle engines very different and, in fact, don't charge the battery as the engine runs?

Thanks