I think it's part of a general principle of making evidence be "clean". A huge paper trail, specific needs to define how the evidence was gotten, etc. All of these make it much harder to do things like forge evidence.
Evidence gotten through illegal means also get a lot of doubt just by default. Imagine a police officer paying somebody to steal evidence for them. The person now how has an incentive to forge evidence.
An important detail of this system is that evidence brought to the table cannot be trusted without a transparent system. Defendants will almost always contest evidence, but this system makes that argument hold a lot less water.
(There's still the issue that police might not be interested in collecting evidence that goes against a prosecutor's case. Don't know how that's solved)
Evidence gotten through illegal means also get a lot of doubt just by default. Imagine a police officer paying somebody to steal evidence for them. The person now how has an incentive to forge evidence.
An important detail of this system is that evidence brought to the table cannot be trusted without a transparent system. Defendants will almost always contest evidence, but this system makes that argument hold a lot less water.
(There's still the issue that police might not be interested in collecting evidence that goes against a prosecutor's case. Don't know how that's solved)