The hygiene thing may have been a practical benefit, but it certainly was not that reason. As has been stated above, Incense was used hi Jєωιѕн worship before the CHurch and symbolized our prayers rising to God. It also engaged the whole body in prayer, including the sense of smell. I have never heard a Latin rite person observe this, but it is frequently identified as part of the reason we use incense among eastern rite Catholics.