Who says they don't? People living on state benefits may yet have things they are passionate about. Their time is spent doing something, and sometimes that is something good for society, even though it isn't immediately profit-generating.
Living in Finland I met a man who was perpetually on the dole, but he was an extremely active Wikipedia editor, for example. I have often thought if that basic income existed, I could finally do some of the huge OpenStreetMap expeditions I had in mind (adding house numbers for the entire surrounding region, for example.)
Yes, some unemployed people might turn to drink, drugs, or petty crime, but this can be solved by building community infrastructure. The ills of the Parisian banlieues, for example, are often ascribed not just to unemployment, but to the fact that all the cultural and leisure facilities that were promised back in the 1970s were never actually built.