Some programs have decided to level the playing field by not responding to emails or reading through an applicant's statement of purpose until after they have applied. It's one of those "hidden curriculum" things that a prospective student should reach out to faculty ahead of applying, and not every student is aware of this unless you have connections (and not everyone has those connections). One student told me that you may actually get a heap of replies after you actually submit your application, but not as much right now. Some professors may respond and say they're retiring, or going on sabbatical, in an effort to save you an application fee. So don't be discouraged if you don't hear back any time soon.