HC-06 module versus 1sheeld
Why would you buy a car when you can cobble something together from some old pram wheels, a lawnmower engine, some old scaffolding, gaffer tape and chewing gum?

Because buying a car is considerably easier and more reliable.  Plus your "friends" don't laugh at you when they see you trying to drive it to work.

Yes, you could cobble something together that might work using random components and other bits of software, but the work involved would be considerably more than plugging in a shield and downloading an app that is guaranteed to work perfectly with that shield.