Crypto is both and it will depend on how you look at it but let's look at the fact that all of us treat it as an investment. No matter how an advocate you are of wanting people to spend their crypto for purchases. You can't stop anybody by telling them that it should be spent. The value of it is volatility and because of that, stopping them won't help and instead, they'll do the opposite of buying more because we go back to what the first reason is, crypto is now majority's investment vehicle and that's what we treat it like.
Not everyone has the patience to wait for their investments to start making really good returns. In Bodo Schaefer's book The Path to Financial Independence, he tells of a case where a young man under his guidance learned to save and invest in order to eventually become financially independent, but at some point, he simply decided to buy himself a new Porsche with all his savings. The same goes for people who perceive cryptocurrency as an investment, not everyone has the patience to wait until their investment makes them rich, someone will spend it much faster and it doesn’t matter if it is fiat or crypto.