Ummm... because some of us have lives...
And although I do strongly believe that you should try and create the perfect environment for muscle growth during the 2 - 3 months you're ON cycle, it's unpractical, and almost IMPOSSIBLE, for the majority of us AAS users, due to business trips, etc..
And vacation.. going away for a couple of weeks.. same thing. no need to knit-pick at the details here.