I've noticed this.
Was pretty surprised.
While awake can you really forget to breath? I thought it was impossible, but guess if the brain is really focused on something, can happen.
Doctors aren't always right, of course, but my respiratory professors said that the desire to breathe is largely based on mechanical sensing with a lesser effect based on O2 and CO2 in the blood.
If you lower co2 levels and then use oxygen, your co2-triggered urge to breathe will be delayed. Sometimes it’ll be delayed until you’re hypoxic, at which point you could pass out.
This happens due to hyperventilation in free diving (and other reasons, though this is the most common). You exhale more co2 than you would while breathing normally, then dive deeper or longer than you should because your blood isn’t the correct chemistry to trigger an urge to breathe when it should.
So I don’t think people forget to breathe, but it could be that we substantially delay breathing sometimes and it seems out of the ordinary, longer than someone normally might, and therefor strange. But maybe it’s not? I’m not sure.