Questions to Hard Money lenders

[Ori Rauch]

Dear BPs,

I was hoping to get some insights from HM lenders or from people who work with them frequently.

I'm struggling to understand why someone would agree to pay 12+% for loans where you can get mortgage at ~4% or other loans at much less than the rates of HM.

Why don't house flippers who's doing that for quite some time now (lets say did at least 5 rehabs and can present successful track record) go to the bank to get line of credit for financing deals and rehabs in return to first lien mortgage?

We are looking at a significant difference in the cost of financing the deals, 12% vs. 5% on a 300K for example is more than 20K difference a year, not to mention upfront points and other fees.. 

So what am I missing out? 

Every thought is appreciated.