And it might be a way for homeless people to retain some control over their ID that cannot be taken away from them, unlike an ID card, or a Yubikey, or a piece of paper with their 2FA recovery codes, or a smartphone, etc
Also, people may want to be identifiable, and/or they may want _not_ to be identifiable. Abstract wealth---having possessions tied to ones identity---would seem to skew the balance more towards the former. Homeless people may be more likely to want the latter. The problem being pointed out here is that this system makes the latter more difficult.