I suppose there is not a definite reason, but the two comments provided seem reason enough. Seeing as these three games were a sensation in there time as an introduction to the world of the DS (which stands for dual screen), the touchscreen factor of the DS was widely admired and, as LightRoserade's comment presented, was being emphasized. Another, rather simple explanation for this is as sumwun suggested, a thing to do in between animations, for people who didn't find them extremely fascinating.