It's absolutely not impossible.
The people who are using are adults. As other witnesses have said, you'd be surprised at the degree to which there is a spirit of co‑operation and solidarity on the street, even when it comes to overcoming all the realities these individuals have to deal with. This is especially the case for the homeless people we're trying to reach. They need to figure out how to find something to eat.
These individuals are able to make choices. The problem that arises is often related to the lack of choice or the lack of resources that would enable them to make choices tailored to their reality and needs.