"Hai" is redundant here. You can also say " tel namkeen nahi hota"
Why hota is there...?
When you are stating general facts, you use hota hai
E.g : the sky is blue
Grass is green
Hota hai......does not ?or is not?
I'm not sure what you mean but what I can make out from your doubt, Hota Hai literally means is / does happen it's the "nahi" which makes the sentence negative