Trains in Japan cease operations during nights, and last stops of trains move progressively towards core Tokyo to position vehicles for morning operations. This means you can't just stay at the table until stations close and catch the very last one, but people have varying time limits for train rides home.
So binge drinking train riding bar goers has to know the absolute latest time they must give up their mugs, which they're going to miss anyway, but will still try anyway, to be stuck mid-way to queue up for a taxi. Or they can be smarter and get stuck at Shinjuku, queueing for a taxi. The smartest ones hit 24/7 places like McD, karaoke, or internet cafe. Or get couples of cans at 7-11 and raid a friend's apartment. None of them are smart, they're all drunk.
I've never taken a taxi in that kind of situation, but I imagine the experience wouldn't be great. Waymo at midnight is certainly going to be a game changer to them.
Where I'm from, where the rail services when they stop for the night, have _some_ replacement — you might need to wait 30 minutes for a bus, and then ride it along the U-Bahn tracks and the trip will take 45 minutes instead of 15; but there is _a_ way to get home before the trains resume.
Just coming home is difficult.
Seriously, if I stay out drinking past 1 I don’t generally care any more whether I stop at 2 or 5am.
Living in Asakusa, meeting up with friends that live in Tanashi; and drinking in Shinjuku — nobody is able to walk home. We either stay out all night, say goodbyes at ~11PM, or the party moves to Asakusa (we have a relatively larger place).