That's sort of the answer.
In a small capacity engine the turbo won't spin up as quickly as in a bigger one so the supercharger will fill the hole in the bottom end of the power curve (emissions come into it a lot too).
In a bigger engine, say 2.0, the extra volume of the exhaust gasses can spin up a modern light pressure turbo from around 1500rpm hence the added expense and complexity of the supercharger isn't really needed.
Horses for courses.
As an example using Diesel engines as they benefit the most from turbo charging, a Polo 1.4 TDI has almost no power below 2000rpm but in a large truck with an eff off huge capacity engine the turbo is spinning nicely from around tickover and it's all over and done with at 3000rpm give or take.
Then again I could be talking out of my arse!