Why you are thinking that people will lost their keys? I don't think so that it will happen to all of us, though I can't deny that it will happen.
And holding is what I wanted to say too only if he has a stable source of income and can sustain the things that he needs with his other source.
Or else, holding is not for him and he can have a choice with trading which is a good one.
There's this thing called death and if you didn't leave your private key to someone before you die, your bitcoins are lost forever. There are also times when you forgot the password of your online wallet and if you're using online wallet, you don't have the private keys. They will be lost forever unless the online wallet that you've been using got hacked and the hackers get all the money by having access to everyone's private keys using the online wallet's database.
And for the nth time, holding does not grow your bitcoins. The value of bitcoin simply increases but 1BTC is still 1BTC after millions of years.
Death is very far and different from saying lost keys. But you are right that there are some cases that an individual can forget his password.
But of course if you are valuing your bitcoins and as well as your wallets, you are not going to forget it and you'll back them up.
By simply printing or writing those information that you need.