using a tablet as your normal cell phone?

So it's this lady at work who uses her Samsung tablet as her usual cell phone. Just wondering how that is possible? I know there's Skype and Facebook calls you can do if you have a data plan on the tablet, but she receives regular text messages and stuff. The boss actually asked her one day y she won't get a regular phone she said the tablet is better. I can see reasons why it would be better....but don't understand why she'd want to carry around something so bulky to use as her normal form of communication. I'm not gonna lie its funny looking.