Taxes - Why do I owe any?

It took me close to two months to install it but I finally did - the 2009 TurboTax edition.

It confirmed what I suspected all along - According to the IRS, I owed taxes on my 2009 income. Not a huge amount. I'm not going to be sharing the food bowl with the cats, and I can still indulge in Trader Joe's chocolate peanut butter cups.

I can't help but wonder why, though?

Why is it that I, a single man with no outstanding debts nor dependents (beyond the cats), who made less than $50,000 last year, owed money to the feds while ExxonMobil, a company whose profits would make many developed nations envious to say nothing of third-world countries, paid zilch, zero, nil, nada, less than bupkiss?

I can't come up with anything moral or legal. (Well, maybe it was all licit but it certainly wasn't moral.)