I see only one reason, why i would want to be early at the seat. its bcs if i am not, my backpack might be placed above but multiple seats away by the crew, where it is then uneasy for me to have an eye on it whilst easy for theives to take and open them, especially on long flights there would be plenty of opportunity like when everyone is sleeping.
but for this case i use locks on the backpack anyway, so that anyone who wants to open it, either opens it where nothing of value is in it thus no lock, or at least has a much harder time than when trying the very same with other bags…
also on longer flights i usually did not have that problem, but that could also have been just luck