This is very often the case. Some places in Oregon have a lax policy of tolerating substance abuse as long as it's not on premises, but many places that offer shelter are faith oriented and they often have a more hard lined approach in addition to allowing open substance abuse usually comes with many other issues (more fights, etc)

I donate my time on the weekends at The Arches Project which is basically a (failed) effort to reduce the impact of homelessness in Oregon. We spend literally hundreds of millions of dollars to build facilities to provide some beds and daily meals and the overall impact it has on solving the problem is insanely minimal.

If you go to the website to volunteer you'll find a PDF that basically dials back their stated public mission from "reduce homelessness and promote permanent housing / stability" to something closer to "have less people die from cold weather and starvation".

Those are great goals, but I think if the vast amount of people knew we were spending hundreds of millions of dollars and accomplishing so little they would (a) be more motivated to reallocate that money better and (b) be less convinced the problem is being solved inspiring alternative solutions.