Why have vendors 2 different panels?

Hi guys

i have created a subscription for vendors, but what i dont understand is if a vendor use a subscription, in his vendor panel domain.com/vendor.php he see a message that he have to pay money.

After that he see the invoice in the normal user panel and he can generate unlimited invoices why?

Why its not generated in the vendor panel? so that vendor have one panel and users/customers have one panel? why have vendors user and vendor panel and the invoices are in the user panel?