shlishi: Minhag avoseinu b’yadeinu. Many people want it “like it always was.” Of course, based on that logic you could ask that given that the practice of baking thin, hard matzos only started in the times of the early rishonim, why do some people insist on using hard matzos instead of soft? The answer is that they feel that thin matzos are better for technical reasons (no chsash of unbaked dough, for example.) Similarly, yekkes feel that machine matzos are better because they are easier to control so we know exactly how much heat, and how evenly distributed etc.
Machine matzos also raise the question of Lishma. Rav Henkin, Rav Kook, Rav Breuer and Rav Aharon Soloveichik (he better have, he was the rav hamachshir of Streit’s bakery for many years) held that kavana had by the machine operator was enough. Others held differently.