Well, yeah.

A blockchain is nothing more really than a database.

The use case is when I don't want or have a trusted keeper of that data.

See, if it's your excel spreadsheet, how do I know that you're not going to change the values on it? For some things that doesn't matter - but for things like funds between different parties, etc, that can be a big issue.

Traditionally this has worked by having a trusted third party - a bank, a court, a escrow company, etc. But all these require lots of effort to have as well, and can be bad actors.