Flew this morning's UA761 LGA-ORD. When we reached gate C27 and fully parked, with engines off and all, the captain came on the PA and said "please remain seated until the jetbridge reaches the aircraft." The seatbelt sign remained on and a flight attendant then came on the PA and asked everyone who, by muscle memory got up, to sit back down.

While it's not uncommon for the captain to come on to ask people to stay seated if we're not fully marshaled into the gate, this was the first time in hundreds of thousands of miles with UA to be asked to stay seated while on the blocks. Anyone know why this could have happened?