That is basically what it is. Thus, as an investor you should take good care of your assets because it would be impossible to recover your funds once you became negligent of it. This is only to remind us that it is money we are using and should gove importance into it if it really matters on your end.
If your private key is lost, your bitcoins are lost forever. There are also some bitcoins that have been intentionally or unintentionally entered into addresses with unknown private keys or using wrong scripts, making this part of bitcoins fall into the void forever. If you can save all data and private keys. Your bitcoins will last forever, even your grandchildren will get the bitcoins you have. Bitcoins are lost forever, but they also exist forever.
Yes just think of that man who lost his hard drive containing huge number of Bitcoin. He regret not putting more effort on keeping it sored which is why up until now he is still seeking for that piece of storage with hopes of being able to get it back but I doubt it will happen. It is easy to secure important informtions and it is on your end how would you do so depending on your lifestyle whethe you are an organized individual or not.