It is the choice of the applicant, provided the family can afford the associated fees or the colleges waive the fees.
My son was in the process of preparing applications to 20 colleges when he got into his top choice early decision. He chose his list (narrowed down from a much longer list), we had visited each of them (plus other ones he had eliminated), and he had interviewed at every one of them that offered an on-campus interview. He had done his research, so he could speak and write knowledgeably about every college and why it would be a good fit for him. I would say there were 3 safeties, several matches, and several colleges that had admissions percentages under 25%. He was determined to apply to these 20 colleges to increase his chances of admission to at least one of them that was not a safety and to have a choice among safeties if he only got into safeties. It is possible he would have decreased his number before the due date, but I do not know. (After the fact, he said he thinks he would have dropped two low matches after getting into his safety EA.) I had suggested he decrease the count to more like 12-13, but…
It was his choice. He was the one who had prepared for all those interviews and would have had to finish writing all those supplemental essays.
My only request was that only the “free” regular decision applications be submitted prior to hearing back from his ED and EA colleges, so that we could save on unnecessary application fees. Good thing, since he was accepted ED!
When you hear the interesting mix of acceptances and rejections that other kids at his college received, it is clear that every college makes the choice differently. Yale may admit an applicant Columbia rejects, etc. This means that it is not necessarily an accurate argument that adding more schools will not mean that you may not get into one of them, especially if you are a fully qualified “typical” applicant for the college. This may be true for an applicant, but it may not be. There is limited predictability. Thus the pattern of kids applying to a huge number of colleges continues!