Why are people saying that iPhone 4 is not flashable to Cricket?

I've been wanting to get an iPhone 4 from Verizon flashed to my current service Cricket, but people are saying it's not possible. Even a Cricket salesperson told me it is not possible, but then he tried getting me to buy the $500 Galaxy S3.

But! I found a cellular store near my house that will flash an iPhone 4 from Verizon to Cricket for $20? I also know a couple people that have an iPhone 4 from Verizon flashed to Cricket.

So i'm confused as to why everybody is saying it is not possible.

Cricket does not officially support the iPhone, and they want to avoid being charged by Apple for supporting it. That and technically, taking a phone from Verizon to Cricket is technically illegal (DMCA laws), and they do not want to be found afoul of the law.

Flash it to metropc. Its better