>So since the users were relatively calm and lucid in every instance, and since it takes such a heavy toll on the body, we can assume that it takes a great deal of concentration to enter and maintain, whereas Vegeta was enraged at the time, similar to Gohan when he first achieved SS2, and then he surpassed the power of SS3 anyway, rendering it obsolete, and the state can also be seen as a precursor to Trunks's rage form, which is also an evolution of SS2, and is at least as strong as SSG. So it can easily be part of the same canon. Now, here's why Goku didn't go SS4...