I quite agree, I've never left early for football reasons in all my years supporting the Albion going back to the 70s, although I'll admit I have felt like doing it on the odd occasion!
I think in West Ham's case, it wasn't just the score line, but the turgid footy that Moyes's teams trot out week after week. You can probably bare it to a point if you get results, but imagine being 4-0 down at half time to Palace with Moyesball, you'd be severely tempted, would you not...