There is reasonable science backing the idea that working out 6-8 hours after you wake up is optimal. But how many people can carve out time at 12 in the afternoon or later to workout? 

There is a lot of evidence indicating optimal protein intake for a 70 kg individual is between 85 and 110 grams. But try getting a person eating 20-25 grams of low quality protein to 85 grams overnight with a complete rehaul in food selection. Spoiler alert: you are much more likely to fail than succeed. 50-60 grams is much more likely to result in adherence. 

Optimal is not always practical. Sometimes sub-optimal is more sustainable. The road to optimal is bridged with suboptimal habits. An imperfect program done consistently trumps a perfect program that one fails at.