A very very high fraction of animals are territorial and will fight to the death over land claims. You can see this in your back yard if you have squirrels or bird nests.
>But just hypothetically, if I want to grab a bike, ride to some isolated forest in France, build a cabin and live the hermit life, I can not to that.
This is actually a result of fairness on the part of the French government - you are a "nice person" and presumably would not ruin the environment for anybody else if you did that, but if it were legal to show up and make houses in French forests it would only be a matter of time before unscrupulous individuals began to show up and clear-cut the forest, overtaxing it and turning it into an unregulated slum city. Indeed if everyone were nice there would be no need for laws or governments at all.