Welcome to the forum, CharlieSierra24!
And you are quite correct... A related note is my own experience, which is that replacing a dead or damaged motherboard with a new (or refurbished) one does not automatically provide the correct serial number.
If not changed, this can lead to difficulty or downright unavailability of auto-identify options on manufacturer websites. WORSE, it could lead to MISidentification of a system and possibly damage resulting from bad BIOS flashes because of that misidentifcation.
Yes, many of us may not actually say yes to those options. But others do, and such a misidentification could be costly.
In short, there ARE legitimate reasons for wanting to change a serial number, even as I'm sure there are illegitimate ones. It's not really up to us to judge. We're here to help or at least share information!
Regards,
O Shadow Fox O