Among other matters:
- Your devices are no longer fully under your control, and don't answer to you.
- Even where DRM isn't itself directly. malware (Sony: https://en.wikipedia.org/wiki/Sony_BMG_copy_protection_rootk...), it inevitably creates backdoors for APTs.
- The legal proscriptions on analysing and assessing ADRM mechanisms create both minefields for researchers and multiply the existing security threat risk.
But most critically, and pretty much fully torpedoing your voluntarism argument, device vendors may be contractually or legally prohibited from producing non-DRM-afflicted devices in their own relationships with DRM gatekeepers, meaning that there are no (or very crippled or expensive) DRM-free alternatives.
Witness ongoing efforts to plug the "anologue hole" (https://www.eff.org/issues/analog-hole) in various devices and software.
FWIW, my complete crap Chrome browser on my complete crap Samsung Android device refuses to allow me to screenshot this HN thread claiming it is a "DRM protected page".
I'd love to replace the device with something vaguely comparable. Between licensing restrictions, monopoly coercion, and market dynamics, there is literally nothing available.
Or more briefly: Your assertion is absolutely unsupported by empirical experience.