It's not healthy to engage in anything excessively as the very word suggests, it's over the normal or average amount. At that point you are headed into addiction forming territory, so you build up habits and can end up doing them like a robot on autopilot every day. It's good to have variety in your life, so if one task is taking up an inordinate amount of your day it is going to be interfering with other things that you might need to do. A problem really begins when you start prioritizing these two "unnecessary" activities over things like basic hygiene or the need to work in order to support a family, even worse when you end up doing things like stealing or other criminal acts in order to prolong your perceived happiness.