Lore has a very important part in any game for immersion, style, and connection to that Self-Realization/Self-Expression that drives RPGs. However, other than playing crucially within Quests and the Campaign ... it should really take a back-burner to Art Assets, and (more importantly) Game Play.
Game Play is what the game "IS" ... and Art Assets are what make up the game. In terms loosely derived from Aristotle ... if you compare a Game to a Chair ... then the Lore is who made it, who owns it, which buildings it has passed through, etc. The Art Asset is the Chair as you see it, its Crafting, its Style, the way you View the light reflecting off of it.
The Game Play then is its abstract "Chair-ness" ... the "Soul" of the Chair, in other words, you cannot see it, yet it exists nonetheless. It is the experience of sitting in the Chair, and while everyone has a perception about the Chair (usually based upon the Art Assets), the center of the experience is inexplicably the "Chairness" or gameplay.
Now, Game Play might be a lot more visible than "Chair-Ness" although everyone has had that Chair that, for one reason or another, they just like ... regardless of a potentially garrish appearance.
The Art Assets are how we interact within the world, and what drives emotional and psychological responses (although a lot of that can be improvised upon) ... while the Game play is something that is forever tied to the game, and makes the user (drawn by either lofty promises or interesting Art) either love the game or hate the game, or anything in between.
The Game-Play is the retention factor, and the heart of the true experience.