They feature prominently at this time of year, not least because their circumstances are so dramatically different to our own, begging and shivering in the cold amidst the bright lights of rampant commercialism and consumerism.
The plight of young people who are homeless is always especially poignant - their exclusion and loneliness at Christmas such a contrast to the incessant images of happy children with their sweets and presents. For homeless young people, even their support systems, where they are available and desired, often dry up for a few days - at the very time when others are surrounded by family and friends.
Not that any of this should take us by surprise, even if it should shake our conscience. Last November, a UN special rapporteur on extreme poverty and human rights reported that the austerity visited by the government on the poor through cuts in benefits and public services was an intentional and callous political act that did not have to take place. He explicitly referred to rough sleepers and homelessness, concluding more generally that for almost one in two children to be poor in Britain is "not just a disgrace, but a social calamity and an economic disaster, all rolled into one".
In Wales, a campaign led by the youth homelessness charity Llamau ran throughout 2018. Called End Youth Homelessness Cymru it has high-level support. Working groups are addressing mental health, educational disengagement, sexuality, and the care system - all factors that contribute to and shape experiences of homelessness.
Once more, we should not be surprised to discover that, beyond the structural causes of increasing youth homelessness, its prevalence is sustained on account of poor integration and co-ordination of services, an absence of sufficiently sustained support, and the failure of policy aspiration - across the policy areas of housing, health, social services, education, care and justice - to convert into effective professional practice. None of that is the fault of those working on the ground, whose dedication often extends well beyond the call of duty.
Shortly before Christmas, Llamau held an Impact event to broadcast just what can be achieved when support is timely, relevant and credible with young people. But getting out of the many vicious downward spirals that homelessness produces is, these days, as much a matter of luck as of strategy, structure and support. It could be so much better than this. Just a few of the royalties from Mud, Slade and Wizzard would certainly make a dramatic difference. Homeless young people need not be lonely next Christmas. It is a travesty that the fifth richest economy in the world should have young people - indeed, any people - sleeping on our streets. We need a concerted effort to eradicate it in 2019.
- Howard Williamson is professor of European youth policy at the University of South Wales