Having attended a couple 10 day courses with a completely bare perception (non religious, never interested in isms and only explored them till i got a firm sense of dogma). I later served a couple courses as well, which experience, by the way, is equally essential as sitting as for "why", one can only experience the answer to that question. However as my practice evolved also did my discomfort. A bit of that feeling like being in a space you dont belong in after a while. Something whitin was stretching and i was insisting on staying contracted. Vipassana as i experienced it is a self revelatory technique. As one sheds... Or becomes aware... So does the technique engage one. After all observing sensation, particularely in initial stages is still done very much with the participation of the conscious mind, despite what is being theoretically presented at the course. Not that onservation is a characteristic solely specific to this layer but mostly due to the same habbit of engaging the superficial mind that makes meditation such an ordeal for most in initial stages. As the observer is revealed, layer by layer, as the conscious is mastered, the technique its self opens to a new form or non-form for more appropriate expression. I will avoid ellaborating where vipassana is for me, for the same reason talking about the experiences is discouraged in general (birthing expectations/desires is a great obstacle; i've experienced it my self whem one good friend and fellow meditator presented me with a blissful experience of a sudden "heart opening" that created much frustration for a me that was still wallowing in physical pain at that time and never since experiences the then described very intimate experience... However gained interesting insight regarding my appearent incapacity to rejoyce in my brothers and sisters success... As the method is not linear, every experience is after all "right" and useful). At a 10 day corse if i well recall, old students are actually gently encouraged to foow their experience rather then rigidly follow rules as beginners are for a good reason required to do.
As for why and how does observing sensation burn away or undo or remove anything at all... It doesent really as the expectation of an outcome is in a sense contrary to the technique its self. When we become aware of a particular thing, the level of our awareness equates with the level of our mastery. Observing bodily sensation we initially will mostly take note of familiar feelings and some unfamiliar ones, subtler ones might appear as a lack there of. Yet as the awareness is sharpened sensations become obvious for which we might not have a name or the point of reference, if any, is vague. As we incorporate these sensations into our awareness, in a progressive fashion as we practice we master not only the sensation but all of its appendages hence reactivity becomes less and less authomatic and much more volitional. In a sense we are de-victimized from the respective mind body unit. So, yep, remain alert, remain attemptive, do your practice dilligently and persistently and all is comming.
As for wether mr Goenka's format of this technique is for everyone... Yeas and No. The Buddhist infusion of the technique might offend some meditators even though it is masterfully mild it still reveals a bit of the teacher's attachent perhaps to his religious/cultural background and i state this with all respect for someone who I gratefully view as my Great Teacher. We are all walkers on the same path. Some atumble around in the bushes, some walk in the light, some take dead end twist and turna from which they must return and some walk under the protection of the shade. In my personal experience perhaps the "only" bizarrery of this technique as presented by mr Goenka, the one thing that scratches my ear is the "this is the only way"... Which might be true or not true it just seams like such anlimiting statent and if i knew no better it would almost sound mildly arrogant to say that one can only master grough a 10 day Vipassana course passed down trough U Bha Kin as well as the constant rhetoric about a particular embodiment of the Buddha (out of its i finite expressions) as the source of this inner woking that seams like an easy onset for a religion specially in our society already deeply conditioned towards religious thinking. Yet all this is dust in the wind that dedicated practice takes care of. I take the usefull and humbly release what does not serve. It is wonderful to be able to practice in silence and comfort for 10, 20 etc days donation based and that is a huuuge contribution made possible by Mr.Goenka and each meditator after all. Let your personal i sight take care of the rest. May all ne happy! Be free! And may the True path be revealed to all as they are ready.