Well, we aretalking here about trading. It's a long way to mass adoption so there is no need right now to put wallet on phone
That's the trick. There won't be any mass adoption in the future if people won't start installing wallets on their phones right now.
Just use antivirus and don't install trashy software.
Did you hear about recent bug in Android? Nobody is guaranteed. Though PC's aren't safe too. The only ultimate firewall is paper wallet and that's only before quantum computers)
So, just don't put your eggs in one basket and have different wallets for trading and hodling.
You are currently right. The most safety method for saving your funds is paper wallet.