By Millin Patel
Well, that is because the disrobing never happened. Take a look at my answer here to a similar question:
Back in those times, the common people would keep their upper part of the body uncovered. The royalty would sometimes wear upper clothes though (uttariya). When draupadi was dragged to court, her uttariya loosened a bit. So she was wearing a top.
Vaisampayana continued,–‘Unto Krishna who was thus weeping and crying piteously, looking at times upon her helpless lord, Dussasana spake many disagreeable and harsh words. And beholding her who was then in her season thus dragged, and her upper garments loosened, beholding her in that condition which she little deserved, Vrikodara afflicted beyond endurance, his eyes fixed upon Yudhishthira, gave way to wrath.”
What probably happened is that after karna asked draupadi and the pandavas to remove their top, they all did so (this includes draupadi). This signified that they are no longer royalty, but just common people.
Draupadi, arjuna, bhima, nakula, and sahadeva were not staked by yuddhistira, but were forcefully made slaves by duryodhana one indraprastha were lost. This is because since they all were citizens of indraprastha and sicne indraprastha now belonged to duryodhana, they were subjects of duryodhana. Since kings have a right over their citizens, they can make their citizens slaves if they want.
Even duryodhana’s best friend, Karna made women and children in anga desh slaves:
“‘Shalya said, “The abandonment of the afflicted and the sale of wives and children are, O Karna, prevalent amongst the Angas whose king thou art. Recollecting those faults of thine that Bhishma recited on the occasion of the tale of Rathas and Atirathas, drive away thy wrath. Do not be angry. Brahmanas may be found everywhere; Kshatriyas may be found everywhere; so also Vaishyas and Shudras, O Karna, women of chastity and excellent vows may also be found everywhere. Everywhere men take delight in jesting with men and wounding one another. Lustful men also may be found everywhere. Everyone on every occasion can command skill in speaking of the faults of others. No one, however, knows his own faults, or knowing them, feels shame. Everywhere are kings devoted to their respective religions, and employed in chastising the wicked. Everywhere may be found virtuous men. It cannot be, O Karna, that all the people of a country are sinful. There are men in many countries that surpass the very gods by their behaviour.’