They are usually constructed of layers of battery material, wrapped in kapton tape or an equivalent, with the entire package shrink-tubed and a pigtail coming out the side for the device interface.

One could easily crush the unit by hand, the construction offers little to no protection from physical forces.

From the tear downs I’ve seen, it seems like the primary motivation for the non-removable battery is so they can cram it into every spare piece of space.

Oh right, the laptop looks pretty and the battery can't be fitted in one area without adding some thickness.

Im so sick over this form over function crap that everyone copies.

Making stuff removable is a lot more work; you have to build a way to hold the thing while it's on, you have to put in connectors, etc. With non-removable batteries they can just glue them on & solder the wires.

Not really saying it's a good thing, but I understand the decision.

Though in practice, the magsafe connector wasn't cat- or human proof meaning when one of those gets as much as near the cable it's byebye unsaved work and in worst case byebye boot because of a messed up system. I ended up taping the connector to the laptop to avoid that. As to why I'd run without a battery: it was swollen.