Parks
The reason no one's mentioned self righting gear is becuase not many people tend to fit it on there boats for a few good reasons, the potential of inverting a leisure rib is very slim so off set against the costs involved the leisure side of ribbing tend to avoid this sort of equipment, then there's the weight of the A frame, bag and canister to consider and the extra cost of waterproofing the engine etc, as someone mentioned before if you do manage to right the capsized boat your engine and electronics are going to be pretty stuffed anyway.
Now rescue boats and commercial safety boats do carry this kit because they have to be able to opperate in all conditions and sea states.
So have you been sold a lemon ? only you can answer that question, do you go out in conditions where your likely to turn the boat over, given that its pretty hard anyway to flip a rib.
Rat