What Drives players in RPGs

Is its lust for loot, novelty of combat,

desire to test their skills?

Nope. Its actually penalty-avoidance behavior:

All the items are gathered to avoid death and

getting damaged: there is plain pragmatic and

non-roleplaying component in gameplay,

since the majority of RPG games revolve around winning

combat, the player who min-maxes, grind levels and over-equips his character gains immeasurable advantage against all "roleplaying"/"social" player(even in abstract terms: the player is faster in game progression in single-player, solo gameplay).

The RPG stat-driven design is anti-thesis to characrer development, with most choices being taken to maximize the stats, as some cosmic accounting joke reducing all viable 'builds' into "cookie-cutter" and "esoteric".