Preamp Power Supplies Inboard/Outboard

Other than the factors of convenience, footprint size, and cost, is there a consistent advantage of an outboard power supply and associated umbilical cord for preamps? It would seem obvious that is it beneficial to separate and isolate power McNasties from the component but are most of the better single chassis units designed to obviate these issues?
Another reason for an outboard PS is, simply, that trannys & other parts don't fit in the main chassis. It's the case with mine...

I assume care is taken to avoid interference in single chassis -- how, maybe Sean et aliae could say
Although care has been taken to shield the rest of the components within the chassis from interference, there will always be some influence, however small. And, as Gregm mentioned above, there can be space issues... Bigger, better, more robust PS's need more room... but not only that, take it further, and factor in heat issues. With electronics so closely huddled together, having an outboard PS, eliminates the need for added bulk to shield the heat. The thinking is that even with shielding, run the component long enough, and it will get hot.