No, totally disagree, sorry. As some of the stories above have proved they're NOT all 'on their arse'. Some have just found a good way of making money They're no more down and out or 'off their heads' then your or I - they're just con-artists. As I said for me the problem is differentiating...
As has been pointed out, they're not all genuine. It's telling the deserving cases (who as you say can't help their circumstances) from the con artists which is the problem.
A similar thing happened to me. A guy, probably in his forties, stopped me down Trafalgar Street and basically gave me his life story. He started by saying he'd just been evicted from his flat as his landlady's boyfriend thought he was hitting on her, then he told me about his failed marriage...