Thanks Garrett, there’s indeed a lot of nuance once you do a deep dive. Isn’t there technically still a third party? Is it really “decentralized”? What is “ownership” etc … That said, the experiential spirit of it is cash: when you buy a piece of gum you don’t need to fill out a form nor does he know/care who you are. You just hand over the dollar. The extra step is unnecessary because he doesn’t need to confirm that the cash was fully transferred. It’s his and he has full control over it. You’ll have to request it back if you want it back. The same way if you lost your wallet. Full transfer of control. Transactions on a blockchain come close to replicating that finality in the digital world. There are pros and cons to that of course— but one pro is that it is much simpler, cheaper and reduces friction.
As far as the the transactional security of it — what you describe is actually what a blockchain, especially the chain, solves for without a central keeper. There are definitely ways to attack it (51% attacks, DOS etc etc) and ways the system mitigates those attacks whether through cryptography or game theoretically. I would recommend the free Princeton book https://d28rh4a8wq0iu5.cloudfront.net/bitcointech/readings/princeton_bitcoin_book.pdf for a full deep dive on that.