My name is Shomprakash and I'm from the Dell Social Media Team. I checked your question and I must say, that is a very good question.
We do have a reason for not including 3G (WWAN Card) on L702X systems built with a 3D screen.
The 3D Screen specifications do not allow further room for the Aerial cable asembly required for the 3G card to work succesfully. These Aerial cables run through the LCD back cover on non-3D models and enable the WWAN card to work with the required signals.
This is as per design. However, i would suggest you to use a USB dongle from the respective service provider for enjoying 3G level connectivity on your machine. I also want to congratulate you on your choice of product. The 702X is an excellent machine when it's about 3d gaming. Wishing you a wonderful time with your Dell machine!
I hope this helps. If you have any followup questions, Kindly reply here. I'll be glad to assist you to the best of my knowledge and ability.
Dell Social Media Responder