open ports are necessary for communication. Open ports are ideal for phones. Apps that open ports are expecting communications of some sort and as long as they are updated and not full of bugs, it is not a problem.
In a server environment when the entire role of the system is to act as a server, you close all unneeded open ports not pertaining to that role because what is important is what is listening on the open port. When you have something not needed listening, you are not only chewing up resources the system could be using to serve should the need arise, but allow attack vectors that are not monitored as closely as the processes critical to the serving and it is easier to overlook security flaws. However, this is a different situation than what is essentially a multi purpose desktop computer where you install software and expect it to do different things at different times. If what you install needs a port open, it isn't a bad thing unless what you install is insecure or malicious.... That is where the problem is- not the open port.