Despite Telstra's faults (that said, none of the telco's are perfect, are they?), I kind of agree with this decision.
If you've got less money going Telstra's way because you open up the network to the competition, what incentive will Telstra have to continue to provide tech service (as someone has mentioned) to the rural/remote areas, and continue to expand their network in these areas?
Yes, it does get a little more complicated when you bring taxpayer funds into it, but a business will always think like a business.
For now, if you want to enjoy the benefits of Telstra's services, you have to go with them (or one of the telcos who are already "resellers" on their network). Unfortunately I think it does kind of make sense - support the service that serves you best, and hopefully they continue to meet your needs.