Most income tax breaks are specifically designed to benefit married couples with kids.
Single people who make a middle-class income and with no kids get taxed the maximum amount and it's really hard to save anything when approximately 50% of your income is instantly grabbed for federal (25%) and state income tax (8%), social security and medicare taxes (7%), states sales tax (6%), gasoline taxes, property taxes, excise taxes, etc.
I've seen newly graduated single people employed on their first real job go into "sticker shock" when they see how much is withheld from their paycheck. A few have cried.
I finally bought a house post-bubble and have a nice modest tax write off. My ONLY tax write off.
Single people get slaughtered on taxes, unless they are in the 47% who pay no taxes or on the dole.
Which is not to say that married couples don’t get hit hard by taxes as well.
I have a friend who both he and his wife work as contractors and both pay their full Social Security amount of 15% or so, so they are getting killed from that.