Q. See question above. As the Rov mentioned, one complies with an additional or many great mitzvos wearing another taalis kattan. If that is the case, why do we not find Rabbonim and even Gedolim wearing more or many Taaleisim Ketanim? Should not all of us do so?
A. It could well be that in order to comply with the mitzva, one has to feel comfortable and enjoy wearing it.
During summer days or even in our winter heated homes and work places, it may be bothersome and annoying, and one may not only resent and dislike the additional clothing and thus not have the right intention now, even for the original one he was wearing. Besides, the many threads and cords of the additional taalis kattan, may likely entangle, twist and snarl with the original ones, thus creating complicated issues for the compliance of the mitzva.
Rabbi A. Bartfeld as revised by, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit'a