The vending machines often have ones with a bottle shaped hole explicitly telling you to only throw bottles in there.

Vending machines do not have garbage cans. If you think they do, you're making a mistake.

Combini have been increasingly restricting access to the garbage can.

They've also been disappearing from train stations, where they used to be common.

It's interestingly a similar dynamic to washrooms in other countries: if only a few places have them, they get harder for those places to maintain as they get used so heavily. So nobody wants to maintain them anymore. On the other hand, when they're ubiquitous, it's easy to offer as a free service, because it will only be lightly used.

Because of the lack of garbage cans, I also reduce my consumption. That popsicle looks delicious but I don't want to walk around holding a popsicle stick for an hour, no thanks.

You put it back in the plastic, fold it up, and put it in your bag and take it home with you.

For some items that still gets quite messy! Especially things like kinako dango, with powder falling out of their crinkly plastic containers that don't seal shut. It's simply something of a deterrent that makes me think twice about if I should buy something, when I'll be carrying it around the rest of the day until I get home.

By far not every vending machine has it and even if it does - it's for cans/bottles only.

Konbini are nowhere close to EVERYWHERE. Just because you went to Tokyo city centre doesn't mean japan is same everywhere

I lived all over Kyushu, in Tokyo, in Nagoya, and in Hiroshima. I lived there off and on between 2005 and 2020.

Most of the vending machines I saw had both types next to them, and I never had an issue with accessing a trash can in a konbini.

I suppose we just had very different experiences.