I actually wondered about that. The reason why you would want to do that is so people can't prepare against you, both OTB or e.g. in the lichess4545 league. Though most OTB players probably won't know your online account (however some people you know a bit might).
There will always be the smart alack with a stupid comment.
The real reason is quite simple. Chess games lie in the public domain for all to see. Internet chess has chosen to follow the policy of Open chess tournaments or casual club play. Anybody can watch the games. Chess is not played behind closed doors, unless it's a private affair. Your chess history is a matter of public record. If you wish for it not to be seen, then you'll have to make different accommodations.