Well the fixed xp gives a steady rate for character advancement. As for not getting scenes while playing well adjusted characters. How well adjusted can a character be in a zombie Apocalypse or having, become a vampire. Either of these are fertile grounds for role play even for normal characters. The scene I was talking about specifically was WoD where your character isn't supposed to tell their loved one about them becoming a vampire. This should cause tension for any well adjusted person. Unless they are a lone wolf they have people they could be hurt by this and are not allowed to know about it.
Yes, there should be tension involved, however... What you end up with is the guy who is just trying to cope loses out in XP compared to the guy who has a tragic backstory that he can rub all over the game.
As for WoD - that only really matters if you're a vampire, or maybe a werewolf. Alternatively, the first rule of vampire club is "you're dead Dave" - cut off contact with your loved ones and move; you can't afford to have relationships outside of the new vampire society you're part of.
The ST should allow and encourage you scenes like this. You don't have to have direct external opposition to tell a story. Also your example is not what the pathfinder core rulebook defines as worth awarding experience. The closet it comes is stating that role play challenges have the same CR as the party level. There are no further definitions or examples. So I guess the gm could award experience for roleplay but how? If I am in a scene by myself do I get xp like I had defeated a cr of my level by myself? Don't forget the wealth by level I am not getting in this example. Also by the fact that the gm is supposed to set those up and is given very little (half a paragraph) in the way of instruction and given 3 paragraphs on how to set up combat encounters and told by the rule book that combat encounters are the most common of encounter it seems clear where the games focus play. WoD tries to focus on exploring your character, and PF/D&D focuses on tactical combat.
Bad criticism here - look at how much more there is on powers and combat in WoD than how to play a character, or how to set up "social" encounters. They expect you to now how to play a reasonable person, just the same as D&D expects you to know how people act, with notes in the various races about how they act differently to humans.
So, if a RP challenge has the same CR as the party, then you get the normal XP, divided by the party, as for a normal encounter (~300XP per level if I remember my charts). The wealth per level that you lose out on this can either be built into the adventure, so perhaps a treasure has slightly more coin in than you'd expect, or can be rewards (or payment) from someone you're talking to, depending on what the RP encounter is. For example, an RP encounter might result in the person you're talking to sending you to meet a friend who knows more than they do, who "happens" to have some resource or other that they can give you, or to provide access to something useful - it entirely depends where things stand.
And yes, I agree that WoD is supposed to focus on exploring your character, but it tends to devolve into combat or use of powers (whether combat related, or presence/dominate type ones). D&D focuses the advice on combat encounters because those are the harder to run with no guidance.