I see 2 possible reasons for your use of the word "unfortunately" (aside from the lifespan of paper vs. metal, which you have already pointed out).
All the paper used in the production of US paper money comes from one single supplier: Crane. I have to believe that there are some back door dealings and political motivations for choosing this supplier, but I don't know any details.
Paper is not worth anything in and of itself. Coins at least have some value in the metal used.
You have just received an A+. Totally correct. Someone told me that Crane belongs to the Kennedys, but I don't know for sure.
That may very well be true but people continue to choose to use paper dollars over coins as well. Dollar coins have been available many times in many forms but for some reason people still seem to prefer the paper dollars. The coins don't circulate as much. True, the government could force the issue if they really wanted to. Personally, I think paper money is more convenient for larger denominations but a dollar coin is preferable to a paper dollar.
That's a good point. Convenience plays a big role. That's why the autopay mobile apps are booming now. Just think when cryptos get more user friendly and accepted by merchants. It'll be a whole different world.
That's the big thing standing in the way for crypto. It depends entirely on you to keep it secure, not a bank or some other entity. It is very, very easy to lose huge sums of money if you are not careful, not only to theft but by losing your keys/password, not making backups, or just by accidentally typing a wrong number. Until there are very convenient ways to take care of these things, crypto will not achieve mainstream success. Convenience cannot be underestimated.