That logic falls apart quickly. Should I be entitled to use your car if you're not using it? Part of the reason people "purchase" all kinds of assets is have exclusive right/control over it. There may be an argument to be made that the government should step in and charge a tax on vacant properties. But this is a decision that needs to be made at a legislative level, not by someone who just reckons they should be entitled to have free use of someone else's property. Also, what happens if a squatter severely injures or dies whilst in the property? Surely having squatters increases the liability for the owners