Because my “productivity” as you call it directly benefits the health and happiness of those around me. Likewise, it is impossible for you to eat modern food, live in a house, and go on the internet without directly benefiting from the labor of others.
I think it is, by definition, selfish to benefit from the labor of others without giving anything in return, if it’s at all possible for you to do so. You clearly have the mental and physical capacity to argue with internet strangers, and therefore you have the mental and physical capacity to carry out at least some labor.
Not at all! I think it’s enough for everyone to contribute according to their abilities. You’re making a living using your skills instead of mooching off of others, and that’s more than a lot of people can say.
I also believe that the vast majority of work benefits human society in some way or another, even if it’s sometimes harder to see. As long as there isn’t a scalable alternative to plastic, people need it to meet their daily needs and standards, and you contribute to that directly.