A lot of it has to do with recovery. If you were to train the same muscles everyday, you would not be allowing the proper recovery time that your body needs to repair and build muscle tissue. You can also run into overtraining and injury when you're not giving your body enough rest. This is especially important when it comes to high intensity training like HIIT, or when lifting heavy. Generally, the higher the intensity of your workout, the more important recovery is.
Incorporating HIIT into a basic strength training routine should be OK, as HIIT is a good form of cardiovascular training that preserves muscle mass better than longer, low intensity cardio.
Some of the bodybuilders on the forum would probably have some better input as to whether you can actually GAIN muscle, while incorporating 2-3 HIIT workouts in a week. Any thoughts anyone?