The other day I set up a post for a client that required tagging a few other public pages. I did this on four platforms and one website. It took about 20 minutes because I customized each post for the platform it was running on.
A lot of people would have set up the post on one platform and had that pushed to the others. And it would have looked good on the first platform and would have been a mess on all of the others.
None of the tags would have worked on the secondary platforms. And depending on what was used for the primary platform (Facebook, Instagram, etc.), the posts on the secondary platforms would have been cut off mid sentence, the photo would not have formatted properly, and either the post would be missing some key hashtags or it would have been filled with hashtags that were useless and just added to the mess.
I see that kind of thing all the time.