>>genghi+(OP)
I've been a CTO (with a lot of pre-sales engineering responsibilities) and a VPE responsible for engineering - sales relationships; I've participated in hundreds of prospecting and customer calls and many years of sales planning/strategy/deal review meetings. I can tell you from first hand experience that sales (and marketing, to a large extent) are both strictly measured and held accountable to forecasts. Forecasting a buyer's behavior, or a lead gen pipeline, or deal timing is not easier than forecasting the construction of a new feature.