It would be nice but may increase their cost. Anyway, while conducting any search, be it at EF, ITA, Google, or even non-travel stuff at Amazon, I like them to search a little beyond my parameters, just in case it uncovers some exceptional opportunity. If not, I can always ignore these extra results.

The classic case is someone who thinks he prefers a nonstop, but hasn't paused to consider if that preference would hold in case a 1-stop was available at ½ the price? Similarly at ITA people get carried by powerful advanced routing language: one might specify 90 min minimum connection time, but again would one have really minded an 85 min connection at ½ the price?

That's why I want such services to provide information, but not make many and if possible any judgment calls. For judgments I prefer the buck to stop with me---and before stopping, keep moving to me.