I've read the discussed reasons on various websites, but it seriously bums me out that I cannot play after the game ends. It just seems like a ridiculously stupid decision. Consider this a petition to be able to play after the game ends.

can't do petitions

http://hometowncolumbia.files.wordpress.com/2007/12/lol-cats-cat-shakes.jpg

Thanks, but no thanks.

Why don't you just play before the ending? What's the difference, honestly?

Its brilliant [IMO] and necessary in this case.

Just build a new (completely different) PC and see how the game plays out the next time.
(This is how the entire series always was BTW)

Na I'm good thanks, you do get a message telling you when you're about to take on the last mission and the majority of the map is still available to you. Just make another save and mess around on that.

Nah, it would be pointless! Whats the difference between roaming before the ending and after?

Yes, we don't allow petitions on this forum. If you want to discuss the game's definite ending, there's already an open thread for that, http://www.gamesas.com/index.php?/topic/1140866-i-was-very-sad-when-fallout-new-vegas-ended-like-fallout-3-did-before-the-broken-steel-add-on/.