This topic wasn’t there for you to conveniently request tags before. Now it is, so if you really want to add tags now it only takes a minute to request it. Quicker if you have this topic bookmarked and know about ctrl+v.
Not every user being able to create their own tags is pretty much how the internet works. Go to stack-exchange, your favorite porn website, or anywhere else and you can usually only choose from pre-existing tags.
Also with now just a few regulars and leaders being able to create tags, there is still a significant learning curve. Imagine the mess if everyone was able to create tags. They wouldn’t look through the tags already available and would just create their own almost every time. That would be bad.