However, it is really sloppy software to generate superfluous pings. If there is not data to transmit, then there is no reason to waste battery power and bandwith to see which server could take your call if you had a payload to send, like a sign on request.
Not if you look at it from the standpoint of the vendor who is selling a subscription service to monitor engine data during cruise. They would want the connection to be robust and available without the customer having to configure anything if they did purchase the package. A check ping every 30 mins is not overkill in this case. The ping also includes the aircraft's digital unique identifier (like a MAC address), so the vendor could activate the service instantly from their server side.
But it sounds like very few folks were aware of the pinging--it was kinda hidden away in the software.
Edit: The pings originate from the Inmarsat satellite system ACARS server, not from the ACARS software on the plane and are sent hourly to check the Satcom connection.