If everyone start storing bitcoin and there is no single transaction for days,all miners will quite mining as without transaction there would be no reward.
Will it not kill bitcoin and make it useless?
If everyone just stored all of their Bitcoins, then it could kill it. If no one uses it for anything, then there would be no value in Bitcoin as a method for merchants to accept it as payment or for customers to use it for purchases. And it wouldn't have value to transfer funds from person to person. I think we need those to keep it relevant. Luckily it is used on websites for purchases, gambling, and trading, so I think it will survive.
The loss of demand is why Bitcoin should not be treated as a commodity, just sitting there as a store of value, but instead as a currency for daily transactions. If it isn't being used, people can just use other cryptocurrencies, and those marketcaps will increase instead.