Why Do Sellers Obscure the Movement Serial Number?

Alphabet obscures all vehicle license plates on Google streetview, at least in the US. If it was not a big deal to post license plates they wouldn't go through that effort. And I never consider Alphabet/Google to be very proactive in protecting personal data.....it's all for sale. People can decide to be as free as they want with their personal data online, some are just naturally more careful than others. Do what you are comfortable with.