Going to sleep feels like it brings the next day, and if you aren't looking forward to what you have to do the next day....you put it off for as long as possible.
I'm the same too. I know it doesn't make logical sense because it starts a bad spiral, but my body (gut?) is trying really hard to procrastinate sleeping because it doesn't want the next day to come. Rationally speaking I know what I should be doing, but it feels like my mind is not strong enough to fight the emotional/gut instinct.
I also procrastinate bed time. I've always linked it to anxiety (non necessarily in strict medical terms/meaning).
That's my rationale: In the evening the day's over and 'nothing can happen' anymore for that day, so I feel I can chill out. On the contrary, tomorrow 'anything has yet to happen' and I can have a feeling of worry.
That's the reason I've given myself to procrastinate bed time. Not sure of that's the case or I'm just a night owl (possibly that's the case as per Occam's).
Anyway, I feel you.
This is me. For me, it's not about the next day, but exactly about that "nothing can happen" feeling - everyone is finally asleep, no one has any expectations towards me, nobody will be calling me (it's night, it's rude to call people at night), nor will they be texting me (they're normal people, they're already in beds, sleeping). It's the only time my body is able to relax a little. It's the only time I can think about things, without interruptions and the nagging feelings I should be doing something else.
I tried, I tried really hard to give it up, but I can't. Now, with small kids in the mix, the mornings are not even an option.
This is what "revenge" in "revenge bedtime procrastination" is about. That feeling that it's the only time that's actually yours, the only moment of actual autonomy in your life. Everything else is driven by others - working a job, running errands, being there with your loved ones. When it starts feeling like an unending stream of obligations, those few hours late at night are a form of defiance, showing the middle finger to the universe, reclaiming some time for yourself.