In Long brackets in flalign the question was raised as a side note, why a certain reputation is needed to create new Tags:
On the side note: how come this whole "reputation" does not allow me to make new tags? Aren't they suppose to, you know, HELP people?
I can imagine some reasons why it is handled like this, for example to prevent getting a huge load of quite similar tags which would divide the tagging scheme into small samples. On the other hand even new tags that are not used by enough other questions within a certain time span are automatically removed. So there is already some autocleaning mechanism that should prevent too much division.