It's just a protection for yourself. Whether you want it is up to you. Note that comp appraisals are only one thing a bank uses in determining mortgage eligibility, not the only thing. It's not a trivial process like buying an ipod or even a car, that's why home purchase escrows are 30 days, 45 days, etc. Escrow may fall through because the bank finds out there are 5 liens on the property or there has been reported structural damage to the site or there is a lawsuit pending on it because a divorce went bad and the kids of one party have put forth a legal challenge to 10% ownership. IOW, due diligence takes time. You can buy a Ferrari in one afternoon.

BTW, getting someone to pull a loan contingency ASAP is one of the classic broker moves as is 'there's someone else interested...you have 2 hours to decide.' You have to understand, a mortgage contingency is NOT a valid reason why a seller should refuse, what it is, is a reason for a seller to FORCE you into making a quick decision on something. Case in point, I went with someone to look at a $1.5 mill property that was on and off the market for over 8 months and had it's price dropped a half dozen times. The broker just happened to also be the owner. He was losing money every day on his loan, taxes, maintenance, etc. as it was vacant. After seeing it and expressing interest, my friend got a call the NEXT day that if he wanted the property he would have to make a decision within 24 hours because there is 'suddenly' an interested buyer who offered full price with no loan contingency. Yeah right. It's still for sale.