There's a fixed (and diminishing) number of police working on actual crimes (that's apart from people claiming to be insulted or offended). Scotland Yard has a shortage of detectives; they're 800 light.
The disappearance of Madeleine McCann, was obviously tragic. But does it really make sense to continue to deploy police resources nine years later?
The historic sex abuse cases; popular stars groping teenagers, or worse, 40 years ago - certainly this is a disgrace, but what about us. Now?
The Rotherham child sex scandal that came to light a couple of years ago, was first looked into 17 years back. If the police deployed on the investigation into Jimmy Saville (I'm not defending him, but he is dead, and so cannot be prosecuted, and is also thereby guaranteed not to repeat any crimes in future) had been deployed in Rotherham, is it not likely that some of the 1400 abused children would have been saved from their awful experiences. To that, add Rochdale, Derby, Oxford, Bristol, Telford, Banbury, Aylesbury and Keighley.
You can't have it both ways. If you want historic crimes (that happened 40 years ago) investigated, there will be less police available to investigate today's offences.
This is important. The murder rate in the UK, for example, is up by 14%. If we can't afford the cost of more police (and the police budget is being cut), then it's necessary to prioritise.
And I think that crime today, is a lot more important than the investigation of Saville.