Can someone please, just answer the question about the weight and balance issues without bringing the east/west garbage into it? I went to nonrev home the other day (PHX-SAN) and was told I could not get on because it was weight restricted. WTF, it was an A319 they have a range of over 3000 miles, right? PHX-SAN is like 400 miles tops. I questioned the gate agent who just repeated "you cannot jumpseat the flight is weight restricted." Finally just went down and asked the captain if I could please get onboard so I could go home. He let me on, but still, WTF? Can someone just provide a factual, nonemotional, non-east/west garbage answer, please? I just want to understand how a plane with such LONG legs can be restricted on such a SHORT flight.