001sky is not making a frivolous point. If all land were private, most of population of the planet wouldn't even have a place to stand, much less to cross. Most populist libertarians are for privatizing almost all public land.

Putting things another way, some people seem to be under the odd misapprehension that "privately owning a piece of land" is tantamount to sovereignty over it. When in actual, complicated reality what one really buys when one "buys land" is a more limited set of rights to possession, use, development, etc. of the land that have been wrapped up in a title. And thus there exist limitations to what one can do with "private property" as exemplified by the fact that other people can get an easement to use one's land for access to their own or might own the minerals under your house.

I was being facetious, but this is actually an excellent point.