At easyJet, seats C&D on the last row are considered to be restricted seats, like on row 1 and the overwings.
The reason for this is that in a pre-planned emergency, the passengers in these seats would be shown how to operate the doors in the galleys, so that they can get them open in the event of the cabin crew at the back being incapacitated. This is the reason why children are unable to sit on these particular seats.