Ext4 snapshot concerns

LVM snapshots and block devce snapshots and need extra space outside of the filesystem you're snapshotting. Try doing that on your laptop - I bet it's not very common to leave ~50% of unallocated space on a device which is not a storage server (or similar).

Filesystem snapshots use space within the filesystem itself, so one does not have to worry about any extra filesystem layout planning on a given server/PC/device.