Actually, not all of them are homeless. For some it is indeed a business.
Yes, and why shouldn't they? It's a free country, after all. As long as they don't do anything illegals, why not let them be?
Yes, indeed. That's why people are indeed looking at concepts like citizen's dividend.
It's vastly amusing that people flock around tv shows like Star Trek which basically promote a lifestyle based on this, but think that their warp fantasies and phaser pistoles are more worthwhile things to strive for than general human decency.