I think it just comes down to this being an extremely conservative field, and these systems get implemented based on past experience.
Before MH370, basically nobody anticipated having to search for a commercial airliner with no idea where it went besides that it was vaguely somewhere within a continent-sized patch of ocean. The 30-day period was considered to be enough. Even with MH370 it could have been enough if the Malaysian authorities hadn't been so unbelievably incompetent as to waste an entire week searching the wrong ocean when they had data which definitively showed it went elsewhere.
It's similar to the question of why airliners don't periodically report their position using GPS and satellite data, since they basically have the capability already. The answer is that nobody really thought it was necessary, since tracking airplanes through other means worked fine right up until it didn't.
Before MH370, basically nobody anticipated having to search for a commercial airliner with no idea where it went besides that it was vaguely somewhere within a continent-sized patch of ocean. The 30-day period was considered to be enough. Even with MH370 it could have been enough if the Malaysian authorities hadn't been so unbelievably incompetent as to waste an entire week searching the wrong ocean when they had data which definitively showed it went elsewhere.
It's similar to the question of why airliners don't periodically report their position using GPS and satellite data, since they basically have the capability already. The answer is that nobody really thought it was necessary, since tracking airplanes through other means worked fine right up until it didn't.