It wouldn't be good at all for bitcoin if wallets offering interest started popping up because within a year we would be going down the same downwards spiral as fiat is.
You see to offer interest on customers money bank are lending your money to other people, would you let your bitcoin wallet provider lend your bitcoins out to another user?

Bitcoin is about taking control of your own money back and if the wallet you store btc in lends it out to someone you don't know then you have lost all control over your money/bitcoins.