I don't want anyone to see my IP except those that have been proven trustworthy enough to know it, sure as water's blue. Privacy, security and just plain practical reasons. I do work online, so anyone who's connected to me (you can discern IP from emails and TCP connections) would be able to link me to this account, meaning they would know that I'm very bad about being drawn into arguments, they would see my opinions on certain topics that I may not want them to know, and they'll see any personal information I give out on this forum, including any usernames that I've mentioned. Which leads to a whole different can of worms. As an example - anyone who is perceptive enough to take note of my writing style (long paragraphs, run-on sentences, information focused logic and didactic reasoning) could easily tie this to my Reddit posts on the DOS2 subreddit, and from there could view my whole Reddit account, which has posts ranging from personal medical information to posts about my past relationships to giving advice to people that are in a bad place similar to what I've been through, and I definitely don't want a potential employer or someone I don't know very well knowing all those things about me. Random people on the internet, I can handle. But my mom? My boss? Someone who I just started dating? No thank you.
I hope this helps to put things in perspective.
