Personally, I felt contacting POI's and receiving a response from them (even if it was a polite, generic form response) was very important to my application process of choosing the programs and POI's I would ultimately apply for. During the summer, I had my heart set on a certain mentor at a program whose research was truly fascinating to me. I emailed her back in September with a brief message expressing my interest. After a month, I never heard back, so I emailed her again in October. To this day, she still has yet to respond. I also emailed my back-up POI at this same program to express my interest, but she never replied either. To me, not hearing back from both professors at the same program was a HUGE red flag for me, so I had to drop this program from my application list.
Meanwhile, I received very friendly, personal, and prompt responses from POI's at other programs that I was initially unsure of applying to, and it was this interaction and attention to potential students that persuaded me to strongly pursue these programs.