As long as your DAP has a digital out you'll be fine ? Unless you are talking obsolete players or boutique DAPs from HiFiMan and others, thats a set of roughly zero by my count .. happy to hear otherwise.
When the QLS-QA350 came along, with a host of outputs including digital, it was pooh-poohed by several on this forum because they couldnt see themselves carrying around SD cards and because it was 'huge'. The HM-801 ? Too big and way too expensive, of course. It seems that we want it all but we dont want to pay for it.
You, in general, are correct. However, it is not as "Zero" as you may think. Of course, more and more Solo like devices (eg Fostex, ipure, istreamer) are coming out making getting digital out of idevices cheaper and easier. Iriver, hifiman, Colorfly, Sony PCM M10 and D50, most mini disc players, and others can and will output digital to a Dac for processing.