They're not interested in building other avenues of revenue. All of their products are designed to collect as much data as possible so that they can feed ever more targeted ads. If they're not getting enough usable data then it goes away and they come out with something else.
That's oversimplifying things, IMO. Any successful business (Google qualifies), is constantly evaluating growth strategy and contingencies. They have made large investments in GCP, for example. That said, they've proven that they're not "good" at anything but ads thus far.