Well for me, with my pipe that is both slow and weird (because it’s 4 ways IP-bonded), VoIP never really worked properly - Mine wasn’t good enough to ship as a professional release grade system - an early iffy beta stage. Audio quality problems and unreliability.
I can’t imagine how it could work for me without serious QoS what with the slowness, bloat and full loading and latency of 40 ms minimum because of ADSL with interleave. But maybe that’s just my ignorance and paranoia.