Hi, although it is quite legal to fly into an AIAA or MATZ remaining 'Radio Silent', I always think it is nice to be in radio contact with someone at all times. Then, heaven forbid if the engine stops, a quick press on the PTT
is all that is required to get your position plotted, for any rescue attempts.
Also those ground stations are good for basic information such as weather conditions, wind speed and direction, and many other tit-bits of news.