banks do not lend on fix and flips...

Look at it like this on 100k loan for 30 years yields the bank $69,800.55 at a rate of 3.9%.
To a banker it does not make sense to loan out small amounts for small periods of time the yield is not good enough for them.  

But people in the private money world make 12%-18% per year on money.

100k loan at 12% for 1 year total interest $6,618.55, the man power hours and paper work is not worth it to banks.