I'm torn, I don't think of Pis as traditional servers and have two dedicated servers on my network. AND I have a half dozen Pis that I use for hosting OctoPrint, DNS, SSH, IoT, Pi-Hole, etc... which are traditionally Server functions.
I tend to think of Pis in terms of single function appliances. They're obviously capable of more but they're so cheap you can just throw one at a single problem and forget about it.