Homeless communities may be unable to take measures to prevent the spread of the virus, but they are not the most vulnerable. The elderly and sick are most at risk, so we must take measures to protect them. In reality, all are under threat of the virus and its proximate effects. We cannot give the homeless special treatment when it already affects so many.
There is a logistical barrier to helping them as well. It would be difficult to implement any policy, such as mask-wearing, within a homeless population. Using extra resources in this way is impractical when so many healthcare services are already being pushed to their breaking point as a result of the virus.