IMPORTANT: do not "store" your coins on trading platforms or in internet based wallets, where you do not have control over it. We are not wallet providers, we provide wallet addresses for withdrawal and deposit purposes for trading only.
Exchanges are for currency exchange only, this is their primary task. They ment to deposit the currency you are going to exchange, than withdraw, or if you want to trade with it, just leave the amount, you are going to trade with. BtcPremium's customers deposites are stored in 100% cold storage so they are not at risk of hacking attacks. The coin payments never go through third parties, they go straight in cold, offline wallets.
It's true that exchanges are potential targets for the hackers, but its users are far more likely to be attacked, who are very often unable to create secure passwords and many of them do not use 2 factor authentication either. If a user's email account is threatened, it is very easy to ask for password recovery. In this case if 2FA is not activated in your account, hackers could empty your wallet in seconds.
Other users connect their mobile phones with their email account, so if someone gets into the phone, can also easily ask for a password reset, access the 2FA code which ends up with an empty wallet as well. Some exchanges allow you to access your wallet on the platform through an application, so you may also be risking your fund if you lose your phone.
How to do
The best practice is to safely store your coins, if you store them in a place where you own the private keys, and have full control over it. For example, a hardware wallet is a great solution for this purpose, becouse the user has to hold the device physically in hand to access its content.
Applications and web-based wallets are comfortable, but you don't own the full control, they don't give you full security.
In any case where a third party has access to your coins, 100% security can not be guaranteed. The contents of your wallet can be stolen, frozen, etc.
If you want to use a mobile application to store crypto, only use an application which primary function is a wallet service, and you own the private keys.
The best sollution for storing and spending your coins is a hardver wallet.