Maybe he can't take it physically. I mean he is 48, at this age he has to train hard and diet to be in shape for the role. But man, that's a lot of money.
I liked his bond movies. Didn't like the older ones i saw (they were to "silly"). This "serious" approach was good. They should try an R rated james bond movie.
Edit... they paid him 2 million for CR, 4.4 for Qos, 10 for skyfall, 25 mill for spectre and probably the same for the next one. almost 100 million dollars. Maybe he is tired of bond
He probably wants to do other projects