1. The Public needs to know if they are permitted to be at a place or not. Or even if they can claim it. Homesteading in the US (claiming public land as private land) only ended in 1986. 2. Because police need to know who belongs at a place, and who to exclude. 3. The government wants to know who to tax for the land. 4. Generally, we think the government's information should be publicly available, not hidden.
Is this a contributing factor to rising home prices? Maybe not, but it does seem weird that we no longer let people homestead public land.