I could be wrong, I am by no means well versed in this, but I think they are limited by appraisals and inspections. If the house gets appraised significantly less than the offer, I believe that the buyer can leave their offer, effectively wasting two weeks of the seller's time. The goal then is to get a cash offer that goes through an expedited process where an appraisal is not needed. In addition, for all of the sellers that believe we are in some degree of a bubble, they want to hurry to sell before it pops/deflates.