Refund amount decreased ALOT after entering gambling winnings and losses

I am confused. I had completed all of my tax return with exception of things I couldn't get deductions for by not itemizing. Therefore, I was using standard deduction.  Turbotax showed my federal and state refund.  However, once I entered my gambling winnings reported on W2-G, then my loses (reported as same amount as winnings although I honestly lost more), My refund dropped, and I owed taxes. The system had me change to itemized deduction, which was now more than double of the standard deduction. The casino did not take out federal or state taxes.  Therefore, I understand why they would have dropped if I would not have added any losses.  However, what I do not understand is that I used money from a paycheck, that income tax had been taken out of.  I used that money to gamble and out of that money, I got some back.  I now have to pay taxes on that money again? I already paid taxes on it once.  It is almost the same as going to a store and buying something and then getting a partial refund. I don't get hit over the head on the refund amount for income taxes.  These tax laws are out of control.  goodbye $6,000 refund and hello $100 refund.