Following a sideline on my wife's tree led me to the question implied in the title. One of her great-aunts married in 1893 aged 32, and that marriage must have been bigamous as she was married as a Smith, although born a McKay. Her first marriage was on Tyneside just after the 1881 census, and 10 years later she was living with her parents again. Meanwhile her husband was in Cardiff with two of his sisters. For twenty years he claimed a variety of trades and appeared regularly before the magistrates for being drunk and disorderly, while fathering 5 children with another Elizabeth, who he seems not to have married. By 1911 his family is in dire straits; the 'wife' died in 1914 of a cerebral haemorrhage, and he is missing from the 1921 census.
However he was still in Cardiff, finally meeting his end in 1923 after being hit by a taxi while walking along the road, drunk. Being known to the police, he was identified and recorded as of no fixed abode; otherwise he might have been an unknown death. So I started wondering how the census records people 'sleeping rough' - where are the forms delivered ?