diago ps09 iso adaptor?

[newperson]

Sorry if this has been brought up before.  I did a search and nothing popped up.

What is the deal with these things, diago ps09?  If you have a noisy power supply why would you buy this product instead of just getting a better power supply?  I could understand if you was trying to run a (-) tip vs (+) tip item and using an iso to only use one power supply, but I really don't get this product.

What am I missing?