So the mobile industry is already past or very soon to be past the 32-bit space with paying customers.

On the other hand, Urbit might never become popular enough for this sort of thing to really matter. We're at about 7 billion people now and the second derivative of the world population is negative, so it should level off at some point. If only 5% of 20 billion people care enough about this sort of thing to actually run a planet, then that'll be only 1 billion people, or a quarter of Urbit's 4-billion address space. 5% doesn't seem unreasonably low to me, either; app.net probably didn't even get 0.5% of Twitter's user count.

And decisions like this might be a part of why it never becomes popular. Elsewhere in the thread people are suggesting that, say, children don't need their own "planet" or whatever it's called, and that they could be one per family and still service the whole world. But that bakes in an awful lot of assumptions about culturally-specific ideas of family and stability of family units. Granted, I think those are culturally-specific ideas Moldbug would love to impose on the world if he could, but this is why people keep saying that even the technical decisions in Urbit are pushing specific political positions of his.

Also, at this point anyone who deliberately designs an address space to be too small to handle already-existing popular things is probably not making sound long-term technical decisions to begin with.

(FWIW I have never seen anyone pay $10 for their planet.)

The reason I ask is if there's a good reason that a bigger address space would be worse in some way, then "bigger isn't necessary" might be a decent argument, but if there's no good reason not to make it bigger, then it's not such a good argument.