1500 passports are still going missing in the post each year, and that's not including the passports that are lost by, or stolen from, their owners.
The plan for registering for a national ID card/passport includes turning up at a centre in order to be interviewed and to submit to background checks. This process will be for nothing if cards are then lost in transit. They could potentially be printed at the centre, but with a target of 600,000 id cards issued each year, this will be a time consuming process.
While passports are falling into the hands of those who aren't entitled to them, some applicants are being refused passports that they are entitled to, due to an assumption that everyone is still in touch with their mother. Expect to see more of this kind of thing as background checks become more onerous.