As much as I hate that there isn't a post-game to DA:O, I do understand why that is. Maybe this analogy will help you understand as well.
A Bioware game is like a cake. It's a perfectly nice tasting cake, and it's spongy goodness is Main-Questline flavoured. Unfortunately, that spongy goodness gets awfully dry and crumbly without some frosting to keep it moist and together. That frosting is made of side-quests and the developers' tears. It keeps your main story from becoming tedious, your environments from becoming linear corridors lacking any point, and ensures your characters can be leveled properly and well-equipped with fancy gear each time they have to face a boss. Of course, when you get to the last few bites of your cake, you're probably going to try mopping up an awful lot of extra frosting with far too little cake, and then just give up because you can't stand to eat a bunch of sugary slime by itself.
Other RPGs, such as your Elder Scrolls, are like pies. These pies are filled with a delicious mixture of interesting environments and a massive number of side-quests. The crust of these games is the main story, because you're probably going to get to it after you've had a taste of everything else, and because it's either going to be slightly burnt and kind of bitter (Skyrim's main questline) or surprisingly sweet and buttery (Oblivion's main questline). But even if it ends up being a slightly burnt crust, you're not going to care too terribly much because you still spent a good while savoring the rich filling of that pie.
So basically, the reason Bioware goes for final boss ==> epilogue ==> roll credits formula is because it makes for better story telling by providing a definitive end, and it's not like you're going to really get anything out of playing those insubstantial sidequests anyways. The reason other RPGs go for the give players open worlds ==> let them run amok ==> give them the option to keep running amok after they finish the main story option is because the story you make for yourself by playing the game, and not the main story the writers proscribe for you, is the actual point of the game. They're two completely different takes on how to do RPGs, both have their merits, and both do things that work for their style of game but just don't work as well for the other.
A Bioware game is like a cake. It's a perfectly nice tasting cake, and it's spongy goodness is Main-Questline flavoured. Unfortunately, that spongy goodness gets awfully dry and crumbly without some frosting to keep it moist and together. That frosting is made of side-quests and the developers' tears. It keeps your main story from becoming tedious, your environments from becoming linear corridors lacking any point, and ensures your characters can be leveled properly and well-equipped with fancy gear each time they have to face a boss. Of course, when you get to the last few bites of your cake, you're probably going to try mopping up an awful lot of extra frosting with far too little cake, and then just give up because you can't stand to eat a bunch of sugary slime by itself.
Other RPGs, such as your Elder Scrolls, are like pies. These pies are filled with a delicious mixture of interesting environments and a massive number of side-quests. The crust of these games is the main story, because you're probably going to get to it after you've had a taste of everything else, and because it's either going to be slightly burnt and kind of bitter (Skyrim's main questline) or surprisingly sweet and buttery (Oblivion's main questline). But even if it ends up being a slightly burnt crust, you're not going to care too terribly much because you still spent a good while savoring the rich filling of that pie.
So basically, the reason Bioware goes for final boss ==> epilogue ==> roll credits formula is because it makes for better story telling by providing a definitive end, and it's not like you're going to really get anything out of playing those insubstantial sidequests anyways. The reason other RPGs go for the give players open worlds ==> let them run amok ==> give them the option to keep running amok after they finish the main story option is because the story you make for yourself by playing the game, and not the main story the writers proscribe for you, is the actual point of the game. They're two completely different takes on how to do RPGs, both have their merits, and both do things that work for their style of game but just don't work as well for the other.
