I found some good cons here:
The noscript element only detects whether the browser has JavaScript enabled or not. If JavaScript is disabled in the Firewall
the simple ideea is in this times your website may adapt to no javascript usage on slow devices using noscript tag like an entity for the entire content of your website**(your html should be prepared to no javascript and all controls must work also if javascript is off,users using basic html controls shoul be able to do everything they done before when javascript was active.So can be the dynamic switch to the same content in other way with the same results=solving the problem wich is the reason the users open your url).**You can see is no matter javascript is or not present ,the website's functionality can be "the same" in any cases js enabled / disabled.On chinese slow devices eg:Samsung neo mini phone this method can run an website without any delays on low internet traffic..
try to run this auto double functionallity website if js is on/off cases:
noscript can change the Internet forever
and to say more on this .. right noscript was invented to work like a trigger when js is disabled but you can work around this feature to change the course of internet functionality about how is now ,to change it's dynamics....