when a game, or anything is minimized when its in full screen, its kind of thrown to the back of the bus of what the processor processes (most situations). and depending on what kind on system you're running, more services are disabled as more time passes in order of what uses the most resources (power wattage/data usage)
like on a desktop, always plugged in, usually dosent disable any services in that situation
but for laptops, they generally turn off services that are idle for a program like disk usage, or wi-fi.
so, are you running a laptop by chance? ^.^