Your point is well taken and I believe the market is beginning to realize that tolerability will be come to be possibly a more important factor in determining commercial success.
However "reasonably" rapid weight loss is important for a many reasons. Here are a some:
If you are paying out of pocket, losing the weight in 12 weeks vs 24/36 weeks might save you $2-3K
If the surprise event you want to go to is in xx weeks, time will be important
payers will care about efficacy as more and more compounds are approved
Market Data 
Markets 
AI
