I'm pretty sure there is some story behind this particular wallet with 310 BTC. You don't just give away your money. Do you know a lot of people who give away money to strangers? I don't. Thinking of reasons why someone could do it:

1. He can't use it himself due to some legal issues (has access to internet but no access to banking, for example). I don't believe in this story that he "is at the point where he does not care about larger amounts of money anymore". It's not how it works. Whenever you have more money, you start making more plans to spend it, and you don't consider that lot "a lot" anymore, thus you always want more. Everyone who went, say, from broke to middle class can prove it.
2. He is terminally ill or crippled and does not care.
3. He is doing it to prove someone some point (e.g. I'll burn my money in a fireplace, but I won't pay for your new car)
4. Maybe he's trying to prove the point that money, in fact, ruins your life instead of changing it for the better? What is this reference to charity? Most millionaires actually DO charity. Bill Gates, Mark Zuckerberg, just to name the few. Are they idiots? I think not. )
5. The funds are somehow locked in this wallet and he does not know the solution in full himself
6. He is actually not allowed to touch the funds (as per suggestion in one of previous posts), so he needs someone else to move them
7. The 310 problem has no solution (and it's not even included in the picture), he just took it himself. Now that the 310 BTC is claimed, why is Mr. Pip not disclosing the solution to the 310 BTC wallet? Maybe because it does not exist?
8. Maybe this picture is only a key to a much larger amount of BTC, so he needs help solving the first picture, and he'll try to solve the 2nd picture himself. ))

Would it not make sense to create, say, 10 wallets 31 BTC worth each? To give someone an extra opportunity? Why is it 0.1, 0.2, 0.3 and 310?

I don't think this could be actually called a "challenge". RSA large number factoring was a real challenge. It provided an incentive to create new algorithms, hardware devices, it attracted people to the problem. But what's the practical use of this "challenge"? Other than guessing someone else's weird riddles? I personally find it humiliating and condescending. I am not a hell of a programmer, but I can easily create a twisted "challenge" most people won't be able to solve, yet with an existing solution. With the amount of computer science knowledge needed to solve this, I'd personally better work on my own miner to live off devfee. At least, I'd be doing something useful.

p.s. I agree with one of the previous posters that this person is probably American. The niceness is probably due to the fact he's not a young person, I think he's in his 60s.