I remember that, and it didn't enter my head or those around me to leave despite the result.
I remember Saints running past the Man Utd fans after 1976, to a mixture of V signs, and polite applause. Saints fans less charitable to Forest in 1979 and at one point trying to pelt them with coins, such was the state of the game and mindset on the terraces back then.
Not sure when all this changed and the lap of honour stopped, but I recall late 90's/early 2000's being appalled by Man Utd whose post match celebrations didn't involve any commiserations with opponents that day or lap of honour but to stand around jumping around like a girls netball team. Another element of Cup Final day being stripped away.