Only if he were alive, and then you'd be right - it would be dynamite.
But the question was, 'why do some people want evidence other than witness allegations'. Answer = because he's dead, because the witness allegations can't be tested, because there is money and attention in it............... etc.
Or because they are genuine and they are finally getting the opportunity to put their experiences or things that they witnessed on record.
As I've said before: if people wanted money from this; they would go to the red tops about it. If people want justice or closure; they go to the police and make a statement. Which is what they've done in this case.
Look at the Hillsborough case. The victims were unable to speak for themselves because they were dead. But witnesses and those who lost loved ones kept going. It took many years, but they kept at it. Not for money, but for answers. For recognition of what happened. For the truth.