I presently own, for the sake of argument, one share of Bank of America. I purchased it through a broker presently owned by eTrade. The custodian for the account is Apex Clearing; they possess custody of the share. The underlying share is somewhere at (IIRC) the Depository Trust Corporation; there may or may not be a physical certificate.

Which is a complicated way of saying that the share that I think I own actually exists in the world, through an admittedly complicated web of commercial relationships maintained by professionals at regulated financial institutions. It is not simply a bookkeeping entry that my broker made up to take my $2. If I sell it, I will likely end up selling it to an internalizer who pays eTrade for the privilege (Citadel?), rather than a counterparty on a lit exchange, but it still exists. It votes in BoA matters. It receives dividends. It seemlessly transfers when I migrate between brokerages, which I have done twice since buying this share. If I wanted to pay an irrational amount of money to win internet points, I could probably even gain physical custody of an actual share certificate.

If you want to nerdsnipe further about the difference between bucket shops, Bitcoin exchanges, and financial institutions, I am happy to go into this topic in arbitrary depth.