The reasons they did not make it the default behavior are multiple, with the Primary one being that they wanted to ensure sales of control panels.

Consider if you had a touch-screen PC and simply purchased an RFX9400 or RFX9600, using fixed IP addresses for your extenders, you could basically do home automation.

The only things you lose are:
1) Cannot run Protected Javascript (.pjs).
2) Simulator will not send IR directly, you need an extender for that
3) Cannot learn IR codes (need real Pronto or simply reuse codes that others have learned or manually enter the IR codes into MyDatabase)