They’re complicated and hard to develop initially, but are fundamentally physically and mechanically simple and thus simple to manufacture cheap at scale. Whereas ICE engines are developed tech but are intrinsically complicated to build.
If that makes sense
It somewhat makes sense, but they are very much not chemically simple? Nor are any of the electronics that are required for safe charging and use simple. That they have simple packaging is largely a distraction from how complicated they are. Just as you wouldn't claim computers are simple just because a chunk of silicon is simple.