many of them consider it more as an investment than a currency
Yeah, i would never touch my stack.
BUT, if it suddenly became commonplace to spend bitcoin, I might from time to time buy a little to specifically spend in a specific store, to sort of support the movement.
Some people buy bitcoin for different purposes, not just for storing alone. If there are available common places where we can easily spend bitcoin, it’s also safer to get a separate spending wallet that can’t be linked to where you have all your stack for security reasons. In case the person attending to you tries to scan the sender's wallet, it’s only smaller amounts that will be inside, and you won’t have to use up something you are holding to give you profit.