I fully agree that making copy of your wallet backup phrase and private keys is very important. Story which you mentioned about someone losing their wallet and offering reward to get it back shows how important backups are. It is surprising they did not make copy which is easy step to take to avoid stress and losing money. I also think DCA is good way to buy Bitcoin but it requires having extra money to invest regularly. However making sure to back up your wallet is crucial and should not be ignored to keep your money safe.
It is necessary and if not, then it is like you are only throwing away your money. You can only hope and pray that nothing bad will happen about your phone and computer where you keep your keys. Losing a coin doesn't always mean that someone didn't make a backup but there are also cases like hacking and fraud transactions (only a few to mention).
So, it's important to keep on learning and stay updated on how to avoid them. Backing up a wallet might be easy for us because we are an experienced user already but not for those who are still starting, though it would be better if they won't start buying Bitcoin first until they already master the basics of bitcoining.