I don't know how tongue-in-cheek you want the response to be so I'll try to play foil and answer it seriously. To summarize, the main reasons are that:
- Cephalopods are smart, but they are not smart enough.
- Cephalopods are not very social creatures. Society is necessary to evolve past a certain level.
A matter of smarts
Cephalopods, octopi specially, have demonstrated a lot of smarts... for a non-mammal. Octopi have very specialized intelligence, with a lot of "brainpower" allocated onto tactile feeling and limb manipulation. They appear to be much better than average at those things.
But when it comes to general brainpower, they are... not very good. Most of the behaviour we attribute to octopi is our interpretation of their behaviour, and not the real motivations. They tend to be very basic creatures, and not very good at long term planning and delayed gratification (which tends to be a better indicator of the intelligence you're looking for -that is abstract intelligence- than the ability to open jars).
More importantly, most cephalopod species are not capable of being self-aware.
Society is the path to domination
Cephalopods are not very good at socializing. There are exceptions of course, but in general they view their similars as competition, with the most territorial species even preying on themselves. Some species have been shown to cooperate on hunting but they do not form permanent social groups.
So, what they need?
Cephalopods would have to develop a more general intelligence, specially on abstract reasoning. We could argue they already have the necessary equipment to deal with a more "civilized" state: They can communicate using skin pigmentation, and they are quite adept at grasping and manipulating things.