I was once shocked by R. Feivel Cohen when he said that someone going on a Chol Ha-Mo'ed Sukkos daytrip where there is no sukkah is exempt from the mitzvah and may eat normally. It actually makes sense: teishvu ke-ein taduru (dwell [in the sukkah] like you live [in your house]). We leave our house to go on a trip so shouldn't we also be allowed to leave our sukkah to go on a trip? Doesn't this fall into the category of hol'khei derakhim (travelers) who are exempt from the mitzvah of sukkah (Shulchan Arukh, Orach Chaim 640:8)?
I have since seen that R. Moshe Feinstein disagreed with this ruling (Iggeros Moshe, Orach Chaim 3:93). R. Feinstein argues that the exemption for a traveler is only for someone traveling for business or some other need, and not just for fun. I heard on Yom Tov that R. Shlomo Zalman Auerbach agreed with this, but I don't understand why there should be such a distinction.
I remembered today that R. Aharon Lichtenstein once wrote on this issue (link). About R. Moshe Feinstein's distinction, he wrote:
In Iggerot Moshe OC II:93, Harav Moshe Feinstein zt"l suggests that a pleasure trip would not be included in the traveler's exemption from a sukka. This inference seems difficult to me.But while agreeing that one is exempt on a purely technical basis, R. Lichtenstein concludes:
One should be firmly and sharply opposed - both educationally and from the perspective of Jewish beliefs and values - to tiyulim or activities organized in a way that involves not observing the mitzva of sukka. The existence of formal exemptions from positive mitzvot is not the exclusive nor the only decisive way of gauging whether to perform them. We do not speak of actual evasive trickery (ha'arama) - itself a significant problem in halakha and belief - and this is not the forum to relate to it. Even not relating fully to a mitzva is problematic, even when it involves ignoring and not evading.
A Jew must be saturated with an ambition and longing for mitzvot and not, God forbid, view them as a burden he is inescapably stuck with that he tries to cast off at the first opportunity. This point is at the root of the trait of "zerizut" (acting with enthusiasm and energy), rooted in the obligation not just to serve God, but to serve him with joy and exhilaration...