Why is bitcoin a fake investment product? Or, to put it another way, how do we even differentiate between real and fake ones. Well, it's easy. In a real investment product, your investment of property or work is invested into something actual, which in the future, can provide you similar benefit. In a fake investment product, your investment is not actually invested into something, but is rather, just transferred from you as a new investor to old investor. Historically, there is no exception to the rule that all such products end up collapsing.
Bitcoin is a replacement for cash. The same you have just said there is the same that could be said about cash? You're investing in something (or earning somethiing) that is just going to not be worth anything in the future but is just a change of state. Your hours turn to $£euro or btc and then you can choose to invest them into other stuff.
the interesting part isn't the currency itself but it's what you could do with the power of the blockchain. It's both overestimated and underestimated in its power. But if we go off current ideas and lots of things such as real estate and stocks are put on the chain, we use the current legislation:
1. You list a house for sale, and allow for viewings, signing your key to suggest you own it
2. Someone makes an offer you want to accept
3. A multisig is entered into with your house, their funds, and two solicitors to authenticate everything (or just a registrar instead of solicitors).
4. The house sale can go ahead if all conditions in the multisig contract are fulfilled. Different entities such as your serveyor and builder could be added to the contract so you don't have to search for/order paperwork.
Similar products such as decentralised finance are becoming available too, such as up to 8%/3%/1% on DAI/ETH/BTC...