I'm sorry to contradict you, but there are dishonest beggars too, that make leverage of compassion.
In Italy, some time ago, they made a report on TV on fake beggars. They were normal people, with houses, jobs and cars that in their spare time pretended to be beggars just to get more money.
I think there are certainly the more 'honest' homeless people. But I do guess where you live. In some areas/countries being 'dishonest/dodgy' is the 'norm' and so it attracts the majority of homeless people to do the dishonest things they do.
In Italy, some time ago, they made a report on TV on fake beggars. They were normal people, with houses, jobs and cars that in their spare time pretended to be beggars just to get more money.