R. Yosef Tzvi Rimon writes about the Ashkenazic custom to refrain from eating kitniyos on Pesach (link):
Do The Various Rationales Apply Today?Also see these posts: I, II
At first glance, one might have thought that all of the reasons mentioned above for forbidding kitniyot on Pesach are no longer relevant today. The truth, however, is that even today these reasons are pertinent. Even today, all types of kitniyot and grains are packaged in the same factories. Thus, we sometimes find wheat kernels in packages of rice, or the like, and therefore the decree should apply today as well. What is more, in recent years food companies have begun to manufacture similar products out of rice and the five grains, such as rice cakes that frequently include the five grains in their ingredients.
Click here to read more[For this reason I am not fond of the idea of Pesach wafers, which look exactly like chametz wafers. While it is not in our power to impose new prohibitions, the decree regarding kitniyot is based on the idea of taking steps to prevent mistakes and deceptions. Even if Torah scholars are unlikely to come to error, the matter must be considered from a broader perspective. When a religious child is seen eating bisli (an popular Israeli snack food) on the street, his non-religious neighbor is liable to think that bisli is not chametz. Furthermore, one should find it emotionally difficult to eat food items on Pesach that look exactly like chametz].
And furthermore, we should add the words of the Meshekh Chokhma (Shemot 12) and the Arukh ha-Shulchan (Yoreh De'ah 115) that the Sages had additional, concealed reasons for the decrees that they imposed, and we must be very careful not to abolish a customary practice just because it seems to us that the reasons for which it had been instituted no longer apply.