The many "exploits" that the game offers and the sandbox nature of FTB makes is so that self-limitation on what strategies you can/cannot go for, go a long way in extending the entertainment value of the game.
Whether it be creating fully self-sustaining/automated systems, limitations on usage of one-block renewable energy, or the strict regulation on EE usage (1.4.7 especially), are such examples.
My interest in the game is being able to engineer systems. Whether it be designing, building, modifying, expanding or upgrading them, it is always a challenge to do so, when certain limits are put into place.