I am not sure if it is feasible, but is there a way to have age-verification only once method on your phone? If you're a sole owner of your phone that no one else uses, can you have your phone age-verified? So you don't have to deal with age verification process every single time you try to access age-restricted information.
I understand your criticism since it seems that you never visited Japan, Tokyo specifically, before. The train/subway entrance gate is open by default. So if your ticket or IC card or phone didn't get registered properly because you don't have enough fund, the gate closes. And there are a lot of people that use the metro during rush hours, and when I said a lot, I mean it is basically a sea of people flowing through. And when those people are trying to get onto the platform, you want to make sure they walk past through the gates like they are just walking on street. Very fast scan with open gate makes it possible. You don't wait at the gate because you don't have to wait for ticket scan and gate door opening.
Also, if you use an iPhone (i don't have any experience with Android phone in Japan so I can't speak for it) to scan, you don't have to unlock the phone to use it. You simply reach into your pocket to grab your phone, and put the phone near the gate scanner as you approach the gate, and it scans instantly really fast (I was actually surprised how fast it was compared to the ones in Seoul). The experience feels like you are just walking through a narrow passage without any hindrance.
I also like your suggestion to remove the gates. When I visited Germany and Austria I really liked the subway there (no gates, and it even operates past midnight!). I saw only one ticket inspector out of probably about 20 subway rides when I was there, but it seems to work just fine. I am afraid such system might be abused in countries like Korea or China.
add: I also just realized that no gate system wouldn't work in Japan or Korea because during rush hour there is no way for ticket inspector to check the tickets of passengers on train. You are squeezed in each train unit like sardines squeezed in tin can.
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