Why buy a DAC when you have a high end pre/pro?

I agree that in some cases this is possible and even preferable, especially for processors that use ADC for their analog inputs. I have a Meridian system that gets direct digital stream from the PC and keeps everything digital right out to the the speakers. If I were to use a DAC, the Meridian would just ADC the signal, only to DAC it again for final output to the amp/speakers.

On the other hand (and in the other room) I have a BAT tube pre-amp with no DAC capability and use an outboard processor there. So it may be a necessity for many a'goners since there's a preponderance of purist, two-channel non-digital gear already in place.

Kjweisner: But I'm suggesting that this a DAC transfer. It comes digital out from the PC or Mac and into the Digital "in" of the processor. The Processor, in turn, does the DAC work and gives the speakers an analog feed. Maybe I'm just not understanding what the need is for ADC. Enlighten me please!
I'll be the first to admit that I am not a total expert.

I've done this for quite some time - PC digital SPDIF output to a Lexicon MC-12 digital in, which uses the internal DACs to convert to analog. Very nice and a minimal number of boxes.

I have recently changed a fair amount of gear and now have a 2-channel preamp without built-in DAC, so I will have to get an outboard DAC. But, I would answer your question by saying if you have a high-end pre/pro with quality DACs, I don't know why you wouldn't do just as you suggest.

More of the audiophile things. Sweeter midrange, depth, imaging, less congestion and so on. As always these sonic features may not be worth the price and hassle but only you know whether it's worth it to you or not.

I found that a $200 Cal labs tube DAC did all these things and worth it to me.