Where do you see frequent trash cans and people regularly throwing trash out in the street?
Typically trash in the street means you don’t have enough trash cans, or a bunch of youth or homeless people whom society is failing.
I have been in few countries in Europe and I see trash in the street. Japan doesn’t have trash bins (not in the street, train, stations) and you won’t see trash in the street.
You are lying or not paying attention. Got to Tokyo and you’ll have plenty (as per Japanese standard) of trash in the streets specially near Shinjuku and Shibuya
And yes they mostly take their trash with them as there are no trash bins. But is it a smart design though?
I am not lying and if you do some search you will find out that there are rarely trash bins in the whole Japan. And that is the result of the 90s terrorist attacks. I have been there and I rarely seen trash bins and I have been in many different cities. There are may be exceptions in some areas but that is not the norm.
Why isn’t a smart design? Why spend money for something that is not necessary. Also bringing trash home will ensure that people will recycle them. Trash recycling do exists in Europe but not in street trash bins. Trash bins exists in Europe because otherwise people will just throw their trash in the street like they do for cigarettes butts.