I wasn't really sure how to phrase the title so I apologize if it doesn't make sense. What I mean by it is I have noticed that now a days, people are less inclined to enjoy the "here and now" of games, and are now more focused on that next level. I remember back in 1st and 2nd edition our group, and other groups we played with, were more focused on enjoying the present adventure whether it was published or homemade and less worried about what our characters were going to get next level. I say it started around 3rd edition with the introduction of Prestige Classes because you were essentially granted a new ability at every level, and got really bad around 4th edition because of all the many powers and power combos. In my own experience, I have seen a lot of people see adventures as just a "grind" and they just want to hurry up, kill everything, and collect the XP so they can level up. It's like these people just can't wait to get to that sweet spot. What happened to enjoying the moment in the adventure instead of just looking forward to that next level? I have even seen mechanics and game design that tries it's best to try and speed things up. It's like the game wants you to hurry up, get through your current character and move on to the next one. I understand that some people only meet for a certain number of hours but not everyone has to worry about this. The game has even lowered the numbers for experience needed to gain levels.
All I ask is what's the rush?
people keep talking like "instant gratification" is a bad thing. why is it bad to want to have a nice thing now or at least get to the nice part quickly?
Or to put Derrens point more plainly- because badwrongfun.
Because instant gratification design tends to devalue the whole product as rewards must be tossed out for pretty much everything to keep the player interested and failure is not tolerated at all. That limits the type of stories you can play somewhat, usually a shallow black & white (doesn't require too much thinking) combat heavy (many fights mean many rewards) railroads (to control the pacing so constant gratification is ensured).
people keep talking like "instant gratification" is a bad thing. why is it bad to want to have a nice thing now or at least get to the nice part quickly? that, like obryn said "You should stick at a level exactly as long as it's fun to do so, and not much longer".

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.