There is subtlety here. Leaving it empty because you are away doesn't mean it's not your residence anymore. Abandoning it changes the legal status of its occupation. Only abandoning the place makes squatting not a criminal offense in most countries.
Such difference exists for a reason, as a balance against an absolute power of owners which drives the number of homeless people up as we can see in certain areas. Take for example the netherlands. It was very common and well regarded to squat for a while, and the homeless population was very low. Now that squatting has been outlawed, both homeless and empty dwellings have gone up. There was some public study on the topic a while back: https://en.squat.net/2016/05/27/netherlands-housing-crisis/
Such difference exists for a reason, as a balance against an absolute power of owners which drives the number of homeless people up as we can see in certain areas. Take for example the netherlands. It was very common and well regarded to squat for a while, and the homeless population was very low. Now that squatting has been outlawed, both homeless and empty dwellings have gone up. There was some public study on the topic a while back: https://en.squat.net/2016/05/27/netherlands-housing-crisis/