iPhone I never heard about Redsn0w

Because it was replaced by the evasi0n tool.

Has to do with the way the jailbreak is done.
Redsn0w was more suited for the older apple devices.

Why update an old tool that does not add anything anymore but takes lots of time and effort from the Devs.

 

Because it isn't. Use evasi0n.

You never know; some day they might bring it back like the mcrib

 

Same reason we don't use windows 98 any more. Newer and better software is out.
You can only update old stuff so much till there's time to replace it with something else.

 

It's because evasi0n, much better jailbreak tool in my opinioon and it has iOS 6 and 7 jailbreaks.