For experiments it is often a good idea to purposefully limit them so that if they do escape they can't become too entrenched. In this case probably the right

For experiments it is often a good idea to purposefully limit them so that if they do escape they can't become too entrenched. In this case probably the right number of address bits would have been 16. That would be big enough to to build test networks (real or simulated) with more hosts than were currently on ARPANET, but small enough that it would not take too long for ARPANET growth to hit the limit. With 32 bits the running out of addresses problem is far enough in the future that someone choosing to go ahead and put the experiment in production is not making a problem for themselves. They are making a problem for whoever has their job long after they are retired. With 16 bits the running out of addresses problem is soon enough that they can see that it might be something they might have to deal with.