I havent been in a Maybach, but Ive driven an S500 and ridden in an S600 and there is a big difference.
I saw the two next to each other at the Museum here at the factory and well .. the wheelbase was at least another foot or so longer, the Maybach is a huge car, it made the S600 look small.
It isnt made to be driven by a normal person, neither is the S600 Guard for that matter, it is made for people who are going to have a driver and want a first class experience on wheels, an office or small hotel room of the highest standard, while being driven around. It is a continuation of their 5-star lifestyle between exclusive clubs and their office or home.
Its one of those things, where if you have to worry about the money it costs, you arent really the customer group.
I could say the same thing about .. why does any human need 700hp .. no one really NEEDs that much power, but thats what makes it damn cool, because it exists for the sole sake of being awesome ... someone driving a Camry cant understand that, just like a poor cant understand why someone would be driven around in a Maybach.