Internal DAC quality vs external DAC's

MHDT RtR Tube Dac sweet sound

I would recommend keeping the digital components separate from the amplification.  

Internal for streamer "starters" or dCs. I see no reason for placing a DAC in an amp except for a sale to a "consolidator." Then one has increased complications for upgrade itis.

So without sounding like jerk, would someone please explain to me why a DAC should not be a part of an integrated box ?

I've read this multiple times but never with clarification as to why.

It's hard for me to believe that this is somehow an issue with the 4 products I've listed in my original post. 

@rockophile221 DACs have a relatively short life of 5 years or less, amps 10 years or more, streamers somewhere in-between.

Separate boxes are best to easily upgrade and elimination of RF and EMI interference.

There are major costs associated with separates, cable costs can be huge because you need additional interconnect, digital and power cables as appropriate for each individual component.

You pays your money and takes your choice.