When we first arrived in Japan, we noticed a lot of little differences which shaped the experience of living here. After awhile, you grow so accustomed to those differences (or learn to work around them) that you forget they are there.
Recently, my husband and I received an actual letter from a former coworker who returned home to England quite some time ago. Since she sent us an actual letter and we're uncertain of how often she checks her e-mail (or if her former address is still valid), we decided we should send a proper letter back to her.
Since I gave up on Christmas cards several years ago, I haven't had occasion to send an actual physical letter for quite some time. Sometimes I send parcels but rarely anything that requires an envelope. I dug around in my long-neglected stationery cabinet and found what I needed and was reminded of a difference I hadn't thought of for quite some time. Envelopes in Japan don't come with the kind of dry gummed surface that you lick (like a stamp) to moisten and then close the letter. They either have nothing at all or they have a double-sided tape-like strip you pull off.
When I first arrived, I was annoyed at having to dig out a glue stick to seal letters and grumbled about how stupid it seemed to be not to have the same sort of adhesive that we use in the U.S. A few years of leftover un-used Christmas card envelopes (from cards purchased from the U.S.) which sealed themselves shut after Japan's long, humid summer taught me a lesson about why designs are sometimes different than those back home.