Well thats the ultimate reason RPGs can offer more then almost any non-hybrid genre of gaming. They can offer more of a 360 degree gaming experience.
Why is this important?
Well we our lives are not linear fight, travel, rest, fight, travel experiences, if they are whoah time to change big time!
And, when we are playing games that last over 6-7 hours or so, any imitation/emulation of the variety of experiences we go through, in gaming terms should be exciting and fun though, is more conguruent with our mind's thinking and processing mechanics and functions.
To put it simpler, Any RPG or Hybrid multi genre game is easier to digest for lengthy sessions, even if broken up, as well as are a perfect fit as far as experiencing reality, and thus games which are subsets, extrapolations, and minimizations of aspects of our reality.
For a person who has not trained themselves mentally to do the same task or limited experience for hundreds of hours, they will enjoy and be more at ease with a game that has a multitude forms of experience like a CRPG(exploring, combat, sneaking, burglarizing, hacking, talking, reading lore etc.) as compared to say for instance playing space invaders for 100 hours.
The limited experience or lack of variety to attract attention makes playing Space Invaders for 100 hours a much more difficult task requiring much more forced steenuous concentration as opposed to playing games like Gothic, Deus Ex etc becuase they have more environmental changes, variety, and depth.
It usually takes someone who has basically trained themselves (i.e. forced) mentally to plod/grind through endless combat for accumulating incremental rewards. These would be the simplest games from Space Invaders, all the way up through Gauntlet, and even Diablo and its clones to a degree, though they have more variety at this level up the ladder.
So those of us who have over the years trained our minds for the arcadish or grind based fun can more easily accept dozens upon dozens of hours of that to play just to get through to find out the whole plot.
But a game that offers some much more on the way offers much more of a mental 7 course meal of satisfaction I would tend to offer, as opposed to the non stop burger fest of hacks like WOW and similar.
Thats why it is easier to tolerate, and more fun to play a well rounded world RPG to get the story then just a hack fest.
