Virgin America and Baggage!

To my knowledge and history of flying in the my country (USA) recently, Virgin America are the only airline not to charge for:
A) checked baggage
B) overweight baggage
I have never been to charged anything for checked baggage or overweight with VA.
Most if not all the other airlines in the states charge for both. Recently i flew from Steamboat Springs to Denver with United, my checked baggage was overweight and i was charged $125!! Flying with American, overweight charge was $50!
I made a flight with frontier airlines recently from LAX to Denver knowing full well my checked baggage was over and on checking in at the kiosk the baggage handler came over and I said to him
'I know my bag is overweight, I will need to pay some more', to which they replied:
'Don't worry about it, just hand it over and I'll deal with it'.
My bag didn't even reach the scales and before you can say bobs your, it was on the conveyor belt on its way to the aircraft. No charge, nothing.
On checking Frontier Airlines' baggage policy, overweight charge (over 50lb) is $75.
Ok, so I got lucky with that flight; how long can Virgin America carry on with their freebie? and anybody else had any discrepancies with their baggage in the US?
A) checked baggage
B) overweight baggage
I have never been to charged anything for checked baggage or overweight with VA.
Most if not all the other airlines in the states charge for both. Recently i flew from Steamboat Springs to Denver with United, my checked baggage was overweight and i was charged $125!! Flying with American, overweight charge was $50!
I made a flight with frontier airlines recently from LAX to Denver knowing full well my checked baggage was over and on checking in at the kiosk the baggage handler came over and I said to him
'I know my bag is overweight, I will need to pay some more', to which they replied:
'Don't worry about it, just hand it over and I'll deal with it'.
My bag didn't even reach the scales and before you can say bobs your, it was on the conveyor belt on its way to the aircraft. No charge, nothing.
On checking Frontier Airlines' baggage policy, overweight charge (over 50lb) is $75.
Ok, so I got lucky with that flight; how long can Virgin America carry on with their freebie? and anybody else had any discrepancies with their baggage in the US?