Why use an appraisal?

[Alan Kahn]

I live in CA.  I want to buy property / business in WA.  I was originally going to go through an SBA loan and they wanted an appraisal.  It now looks like it will be seller financed.  The selling realtor said I really don't need an appraisal.  But, since the SBA wanted it, I figure I should get one.  My WA realtor works with a guy who does appraisals. 

So far I'm not impressed.  He wanted me to wire him the money, but my banker couldn't as he had to many characters for the field.  He also wants 11 pieces of information ... that all come from my research (like past 3 years of P&L or the business tax returns, etc)

So, why do I need an appraisal?