What the difference:cell phone network vs data services?

[fordy]

snakenobi said:

fordy said:
Why would they charge for 10kb of usage (not much at all) when they can charge something like 20 cents for an SMS? Much more profitable!

i get that

 

but can you also explain is there really a difference between gsm,cdma vs 3g,4g

As far as I can tell, the biggest difference moccured between the old analogue to digital switchover. GSM/CDMA is merely competing technologies, and 3G/4G are merely upgrades to 2G (GSM and CDMA).

On a side note, who's not to say that the phone companies already use such technologies such as VOIP on their data layer, yet still charge for the full thing?