"But when you're on the receiving end of such "statistical" ostracism from everyone you meet, it feels quite different."
Do the feelings of the shop owners count?
In fact we already know how this works today, as many employers do not hire criminals and many landlords will not rent to them. Others do, money is money. The system works, criminals don't face ostracism from everyone, they have one another and many non-criminals who are willing to associate with them. (Many criminals are even willing to almost implement your suggestion with face tats.) It provides deterrence of crime and, more importantly, preserves the liberty of the non-criminal population.
I don't care about discrimination of former criminals per se, but making them visibly different might lead to all kinds of secondary crime.
For example, if someone is visibly marked as a known thief, it would be tempting for another person to steal something in a situation where only the two of them had access to the stolen thing, and then exclaim "hey, the other guy is a known thief, so going by the priors, it is obvious that he did it".
This could be further leveraged into blackmail; if you know that you can use this trick to put the former thief in prison with high probability, and the thief knows it too... then you can make the former thief do various kinds of illegal things, giving them a choice between a chance of getting caught doing the actual crime, and an almost certainty of going to prison for something they didn't do.
Shortly, whenever you make a person vulnerable (whether they deserved it or not), you are potentially creating a tool for some predator.
3cousin_it
Because otherwise everyone will gleefully discriminate against them in every way they possibly can.
"But when you're on the receiving end of such "statistical" ostracism from everyone you meet, it feels quite different."
Do the feelings of the shop owners count?
In fact we already know how this works today, as many employers do not hire criminals and many landlords will not rent to them. Others do, money is money. The system works, criminals don't face ostracism from everyone, they have one another and many non-criminals who are willing to associate with them. (Many criminals are even willing to almost implement your suggestion with face tats.) It provides deterrence of crime and, more importantly, preserves the liberty of the non-criminal population.