Tag multi-touch is useless because these years almost all devices support multi touch, and we have other tags such as touchpad or touchscreen that is used for every question with the multi-touch tag.
Also, only five questions with this tag has been created this year and none of them is exactly meaning multi touch, but instead they are about other touch devices which have multi-touch functionality for sure, so no question needs this tag to say something about the question.
Also, we can add the one-touch tag or no-multi-touch tag, because one-touch devices are rarer than multi-touch devices.