git blame is about which author most recently touched each line (in what commit); i.e. is to "blame" for that line having its current content.
You're right in that git blame is most useful for finding which commit touched a line. What was done in the commit is more important than who did it.
git blame is very useful even in a solo project where you already know that you wrote every commit.
There is such a concept as a brand new project not requiring version control until it hits a certain stage: you know it when you get there.
Edit: A large part of the reason now that I think about it is that I don't work off real tickets but just bugs I notice or things that get mentioned on the current solo work project. In a team I can just dissect the ticket and am forced to do only that ticket on the branch whereas solo I'm just jumping all over the place. Sometimes I'll do thing X partway, start considering options and in the meantime do thing Y so it's a mess but the tasks get done so.. For context the project is 1 year old developed from 0 by me. Essentially an internal log parsing and analysis tool for a couple formats. Nothing particularly complex.