This is the point, a local mobile phone user has no great need...

This is the point,
a local mobile phone user has no great need to change carrier,
would you change from your Telstra or, Optus or whatever, if you can save $x per month,
no...too much trouble, I got no time now, I'll check it out later, tomorrow.

a mobile phone punter coming from another country to live here for anything longer than
say 4 weeks, will havechoice but to get a local sim card to avoid charged for roaming - very expansive,
using his/her overseas sim.

Check out , at any one time, how many foreign students and visitors there are living in aus.