No one had asked Loki why exactly he had tried to usurp the throne of Asgard and attacked Midgard. The Avengers were too disgusted with his actions to really care for his reasoning, and the All Father had simply punished him. His punishment, really, was not the cruelest it could have been—definitely not as lenient as Thor, but what was Loki to expect when he was not the true son of Odin?—but that did not mean that Loki was happy about it. If they had asked why, he would not have been punished at all. That was what irked him.
Loki had taken many punishments in his life—some of them deserved, some not—so it didn't really faze him when they sewed his lips together. And how sad was that? He understood their reasoning though, because Loki was the god of lies and mischief, and with his silver tongue, he had gotten out of many bad situations; words, besides his magic, were his greatest weapon. They took away his magic too, of course, by fitting him with a collar—as if he was a dog—that suppressed his abilities—what they did not know was that it only blocked off a portion of his magic, but he would go along with it; if he told them, they would just rip his magic out of his body until his punishment was served. What had been a tad bit surprising—meaning Loki had to use all of his control to keep his expression neutral—was when Odin said he would be going to Midgard for his punishment, and had to stay with the ones who had defeated him; humiliated him.
It was hard for Loki to refrain from rolling his eyes. Odin thought that being in the presence of those who had bested him would teach him humility, and that the people he was in forced company with would help him see how wonderful mortals could be. It probably would have been a good lesson, if not for the fact that Loki had not really wanted to bring the Chitauri to Midgard. Sometimes, Loki thought, the All Father could be quite oblivious. Loki knew more about mortals then Odin thought; it was, after all, quite boring to read the same books in their not-nearly-big-enough library—which were mostly stories of the most glorious battles that held no interest for Loki—so what was he to do other then use his very convenient power that allowed him to travel between realms? Nobody knew of this particular talent, and Loki had never seemed fit to tell anybody—especially Thor, because then Loki would just be used as transportation on one of his honourable quests—because when he would go away for hours, or even a day at a time to various realms(his most favourite being Midgard; they had books for everything there) there were no questions on his whereabouts, no quizzical looks for his mysterious absences, or confused glances when he silently slipped into dinner an hour late. Once again, nobody actually asked him. He never even needed to lie if no one noticed.
So, all in all, Loki was quite pleased with his punishment that was for an unknown amount of time. Sure, he wouldn't be able to speak—what with his mouth having been mutilated—or use his magic in front of anybody, but he very much doubted that they would refuse him books to keep him occupied and out of their hair. They weren't fond of him after all. And even though his punishment would teach him nothing that he didn't already know—why would he want to rule a bunch of whining glory seekers; and why would he want to rule such a troublesome bunch of mortals?—at least he would get to be away from the stifling stupidity that permeated all of Asgard.
Plus, it would be very amusing to see the reactions of the Avengers when they saw their new roommate.