If a tester cannot figure out how to open a door in v0.01, the developer knows to improve the "affordance" or visual cues in v0.02.
Early testers can find "edge cases" where the player might fall through the floor or crash the engine. Snapshot_Dungeon_v0.01.rar
For indie developers, public snapshots act as a devlog, building a following before the game ever reaches a commercial state. The Value of Digital Preservation If a tester cannot figure out how to open a door in v0