Is there any market differentiation amongst stablecoins and why are they so dependent on crypto?

Why are there so many stablecoins and why are they so linked to crypto? 

We go back to basics and outline how crypto started and what it does .

1. The difference between retail uses of crypto and how stablecoins operate. 
2. What's the difference between a retail and a B2B stablecoin - why are there so many?
3. 
   you don't need crypto for stablecoins to work as intended