Cyclone1,
This is because PilotAware provides a 'WiFi hotspot' designed solely for presenting awareness data from other aircraft to your Nav system. It does NOT have an external internet connection, so cannot provide data such as weather etc. from external sources.
To do both, you would need a 3/4G tablet with its own sim card, or you could tether your tablet via Bluetooth to a 3/4G mobile phone and use the phone as an internet access point - though even then connection isn't guaranteed (and is apparently technically illegal due to the potential to cause blocking or interference to the ground based GSM networks - though many people do it).
Hope this helps clarify the position.
Regards
Peter