There are many online wallets like Xapo and Coinbase that do not charge any transaction fees or they pay that fees by themselves. I want to know that how would they profit from paying for their user's transaction fees ?
If no fees is charged then the transaction take a much long time or even might get cancelled !
They clearly survive because they're centralized , when you do something wrong in their eyes they go ahead and seize your coins. It's the wild freaking west man. Don't trust them with your private keys!