But the reason to have XP is to level, correct? So leveling is still the reward. Even in 5E one of the options is to forego XP and do milestone leveling. So hitting that milestone could be a goal.
I thought I was being clear but let me reiterate: leveling is rewarding but not a motivation for me. I want in story motivations that make sense to my PC.
Sure, leveling is the carrot, but having "XP for gold" or even "milestone leveling" affects how players chase that carrot.
As I said, XP for discovery in
Numenera affects how players engage the game, because if players want to level, then they will look to make discoveries so that they can earn XP. Likewise, in order to get XP for their characters, characters in B/X will look to acquire gold in dungeons or elsewhere.
Shadow of the Demon Lord, in contrast, has a quasi-milestone system. It's simply you earn a level if you finish the adventure. But this system is at least more transparent for players, which orients their goals to completing the adventure.
One issue with milestone leveling, IME, is that it is rarely transparent to players, which makes it more difficult for players to set goals for their characters or for players to have a good sense of their character's impending new capabilities. It's often when the GM feels like it according to their whims or even "the adventure says the characters should be this level when they reach this point."
Something interesting about my gaming history and D&D compared to other games.
My group and I have almost always abandoned the XP system of D&D dating back to the 2E era when we first started gaming together. We've pretty much always done some form of milestone XP, although not usually triggered a specific event so much as X number of sessions or "adventures" or similar. The few times we've decided to start tracking XP per the rules, it never lasted and we always went back to just kind of eyeballing it.
What I've realized is that D&D is the only game where this is the case. The XP system is just cumbersome and there's nothing compelling about it, so we just get rid of it. I don't think we're alone in that, and I think the Milestone option being an official option in 5E says a lot.
But in all the other games I've played over the last few years, we always follow the XP/advancement systems.
The end of session questions of PbtA and FitD are a great reward structure. They reward examination of character and interactions with the world and other characters. It involves the players in the process.
Spire: The City Must Fall rewards players for making changes in the city. So it actively promotes what the game is meant to be about. Go out and try to change the situation in the city.
Heart has Beats, which are player chosen goals for every session of play. If they manage to hit the Beat for a session, they get a new ability. This gives players a wide range of choices for what to focus on in play, and gives the GM cues about what to involve in play.
So yeah... I can't agree that RPGs don't benefit from reward structures... I just don't think D&D's has been all that useful for quite some time.
IMHO, XP is easier in a lot of other games because the numbers required tend to be substantially flatter and smaller than the numbers D&D often requires, so XP in these other games feels less like trying to balance the books of a Swiss bank account. Leveling Numenera, for example, requires 16 XP to level: i.e., buying four 4 XP character advancements. That's for all six tiers of play. As you say, questions at the end of a session in PbtA and FitD often deal with smaller amounts: e.g., "1 XP if your character did X, Y, or Z."