Pardon, why not?

In February of this year I explained why I believe that the decision was wrong not to pardon Alan Turing (computer science pioneer, codebreaker, and consensual-gay-sex convict). At the time, Justice Minister Lord McNally stated that

A posthumous pardon was not considered appropriate as Alan Turing was properly convicted of what at the time was a criminal offence". [...] However, the law at the time required a prosecution and, as such, long-standing policy has been to accept that such convictions took place and, rather than trying to alter the historical context and to put right what cannot be put right, ensure instead that we never again return to those times.

I argued that "It is not about trying 'to put right what cannot be put right'; it is about acknowledging, here and now, that what happened to Turing was wrong". A few months after that decision, the Protection of Freedoms Act received royal assent. Part of that Act means that those with gay sex convictions can from next month apply to have them removed from the criminal records database (although presumably this does not amount to a judicial pardon).

So now, I ask the questions: if these convictions are to be deleted from criminal registers, why should these people not also receive a pardon? And if living convicts should receive a pardon, why not also deceased ones -- a good number of whom died through the state's abuse of its judicial apparatus?