Though to answer your later argument, it gave you the ability build relations, prevent vassals from defecting and depending on who you marry, provide you a claim to the throne. And if I remember correctly, there was also a house inventory to store items. That's a benefit to the player to wedding someone. Now if you do not find that a benefit worth pursuing, that is another argument altogether.
- You build relations by catch-and-release, attending any feast (not just your own), and running missions. There is also the semi-hidden method of gaining Honor, which makes all the good personality lords like you by default, even if you've never met.
- Your spouse doesn't actually prevent your vassals from defecting, it is tied to personality types (never recruit ****heads) and their relations with you but ****heads wouldn't attend your feast.
- The stash comes with any castle or town. Or workshop, effectively.
- There are no claims on the throne in native Warband, unless you mean the actual scripted claimants. However you can't marry claimants (or rulers).