In Diablo 3, there is a new super hard game mode, like Hell, but harder!

This mode is called inferno and should be a good experience for people who strive for a challenge and might not mind a few deaths.

With the recent revelation of the beginning of Inferno becoming slightly easier, did the rest become harder in compensation?

Yes, the Acts each get significantly more difficult than they were before when it was all one level.
Sorry, to clarify, the beginning of Inferno is not any easier than it was before. We’ve only made Inferno harder. (Source)

So, what is the incentive for players to fight their butt off in order to get to later Act in inferno? Just to prove because they can?
Achievements. Banner decoration. Bragging rights. … Fun?

I mean it’s like asking “Why do you play video games?”, right? Most of the time the answer is “Because I enjoy it.” and that’s going to mean something different to everyone. When you hit 60 in Diablo III, you have everything available to you in the game as far as game systems go, you’ve beaten the game at least three times already on previous difficulties… why are you still playing?

If you want to hit Inferno and then be happy to just try to farm up a perfect gear set in Act I and never progress, and never want to try to test yourself against more difficult content … well I might ask why you’re building a perfect set, but whatever, if you’re having fun more power to you.

Someone working hard to progress all the way to Inferno (Nightmare and Hell are no picnics) just to stop at Inferno and be happy with just playing Act I and never attempting to beat the game seems kind of unlikely. If you do that’s cool, but it’s a hypothetical situation that I think would be pretty rare because it just doesn’t mesh with why people are playing, or what they need to do to achieve their goals.