It's very useful to figure out who to ask about a particular piece of code. It's also occasionally useful to track down when it was changed (what commit) to give context for why things are the way they are.
Another example: I use the nightly Rust compiler as a library, which have unstable API. git-blame helped track down which commits change the APIs I use when I'm updating the compiler version my project depends on. git-bisect is the other useful part of git for this purpose.
Also if the code is from a time frame before we agreed to stop writing code a certain way, that’s one thing. If it’s new, the person needs some feedback.