Tag Length: Why is the default set to 20?

Is the default length of 20 chosen for specific reasons, or is it merely a guideline?

Out of 650 tags I’ve produced, approximately 180 surpass the 20-character limit. Among these, 100 are between 21 to 25 characters, while the rest range from 25 to 40 characters

I think it’s mostly because longer ones won’t fit in the UI very well.