If You Can't Sell Yourself Into Slavery, You are Already a Slave

 Q: Why can't you sell yourself? A: You're not allowed to sell off your master's property, obviously.
 There are many good arguments for being unable to sell someone else into slavery. There are none against selling yourself. See also: needing special permission from master to be allowed to die. Killing yourself is vandalism against the State.

 Moderns are the most grovelling, servile bugmen ever to wiggle across the planet. 

 You can't marry a woman. The women are all married to the government, who lets you rent one for awhile, and charges through the nose for the privilege. Megapimp.
 As the women are all claimed by the government, naturally all the women's children are owned by the government, who asserts the right to take the child away and do whatever they want with it, for any duration and for any reason. The biological parents are forced to take care of the government's children according to government standards.
 No matter how much you barter, wheedle, scheme, or plot, you can't own land. The government charges you tax, you're renting. The government asserts the right to tell you what you can and cannot build on its land, as it obviously would. Through "eminent domain" the government asserts the right to kick you off its land at any time.
 You can't have your own job. The government charges your employer a (large!) percentage for renting its mortal resources.
 Etc.
 Etc.

 You know, it must be immensely frustrating for the boot. It's trying to stamp on a mortal face forever, and the mortal is licking and caressing the boot. No matter how hard it stamps, the damn pervert gets off on it. "I love a Strong Central Government! Slave me harder, daddy!"

 Admittedly this boot is pretty soft. Very lickable. I should say no matter how hard it tries to stamp; as the limp-wristed population is owned by a limp-wristed leader who just can't stamp all that hard. "Eh! Eh! Uh! Ih!" Allegedly in the interests of maintaining the ridiculous charade of the slaves not being slaves, massa is downright libertine. "You think for yourselves!" """Yes! We think for ourselves!""" "Very good!" """Thanks daddy!""" The women prostitutes are largely free to whore themselves to whoever they want, provided they're 18 when they do it. Certainly the parents have no say, as is meet for slaves. The government could do all sorts of horrible things to its children, but only does one of them. The government's minimum standards on caring for children are quite minimal. As long as you're not a heretic they won't even bother to check. The slaves can slave themselves out to whichever renter they want, and can even choose not to work and get paid for the privilege. As long as the government isn't currently asserting its right to make you fight and die for it, that is. The slaves are paid a pittance with which to buy any kind of disposable trinket they like. The government will approve of the sale of all sorts of useless tat. The slaves can transfer themselves to a different master...provided the new master will accept the hassle.

"Give me your tired, your poor, your wretched refuse, your yearning to be free...so we can ensure they are wholly divested of freedom." As always, slavery is not particularly profitable. Slave owners keep slaves due to  non-monetary motives.
 I would say it's outrageous, but the slaves are clearly having the time of their lives. You guys have your disgusting fun with that, I guess.