So what's the point of the analog inputs on the Benchmark, RME and Pro-Ject Pre-Box Ds2? Tape only, or is a phono preamp presumed?
The analog input allows an analog line level input.
If your DAC feeds a power amp feeding speakers, it gives a path for a non-digital source.
Phono input is special - very low level input signal, and that signal requires special equalization to undo the equalization burned into records. See RIAA curve.
When a phono input is provided on a receiver or other multipurpose device, it will be in addition to one or more line level inputs.
If you have no phono input available, buy a phono preamp to boost the signal to line level for common analog inputs.
That's how it works.