I think most tourist visa's in most countries which are likely to have this issue are at most 3 months. If a country chooses to allow back to back tourist visa's like that then they sort of know what's going on and have accepted it as a net benefit overall. If they don't permit back to back then after 3 months you've got to up and move somewhere else which many people do, but realistically they're not that much different from a tourist in practical terms.