It is because you are posting from a phone. Phones assume all their users are retarded, when only most of their users are retarded. Post from a PC. You know, like the one you are taking the picture of? You can screenshot whatever you want using Windows Key + Shift + S. If that is too hard, and you use Google Photos, you can access your phones on the web by going to photos.google.com. You can then download them and use an image viewer like IrfanView to make sure they are rotated properly before posting them here. If you are on an iPhone, well, just ignore everything I just said and deal with the fact that your pictures are sometimes rotated.