Do you work 60+ hours a week? Have a 45 minute commute to your gym? Otherwise, workouts can take as much as 2 hours or longer. You might currently feel too worn out at the end of the workout to do anything extra, but your work capacity is something that is trained, and it does improve over time. If you have to split it, do the extras later in the day rather than before. Not that doing them before will kill your gains, but you just shouldn't pre-fatigue yourself prior to hitting your main lifts, without a good reason to do so.