PCB information is useful for, among other things, doing board-level diagnostics and repairs of broken electronics to avoid turning it into e-waste.

It can be used to find connection points to signals that would otherwise be inaccessible or at least hard to get to. This has come in pretty handy for the latest wave of Nintendo Switch hacks like Picofly. The scan-sand-scan approach [0] has the advantage over this hack where you can do something like the "kamikaze mod" [1] on the OLED Switch since you know where stuff is, not just what is connected to what.

[0] https://balika011.hu/switch/lite/

[1] https://www.youtube.com/watch?v=LMnS7yfu3Qk (not for the faint of heart)