Stablecoins, I don't get it!

Can anyone explain to me what the point is, of a stablecoin like Tether? I thought the entire point of crypto was that it was completely independent of fiat currency?

Also surely as soon as any bank starts using Blockchain properly, they will effectively have their own stablecoins anyway?

Confused I am!

What about for people who want to hedge their risks against crypto volatility but don't like fiat? How about merchants?