why is it not custom

Apologies, I am not quite sure what you are referring to.  If you are trying to customize the URL of your form, here is how to do so:

https://www.jotform.com/help/261-How-to-Create-a-Custom-URL-of-a-Form

If there is something else you are looking for, please let us know a bit more detail and we will be happy to help.