Nobody cares about a withdrawal here or there. When people have mass withdrawals, we notice. And yes, it does matter. There are 101 different reasons to withdraw from a class and the vast majority of them are things that nobody cares about. On the other hand, dropping out of all your classes means something happened. We want to know, "Is this going to happen again?" History tends to repeat itself. With the number of applicants out there and the fact that we can fill our classes double over with solid applicants, it is a risk to take on someone that has the risk of disappearing mid-training for any reason.
Is this catastrophic? No. Can you still get into medical school? Absolutely. But, it is going to raise eyebrows. When you couple that with a 'weaker' GPA, it makes people wonder if you are going to be able to survive the training. That is not the type of scrutiny you want for your application.