You can benefit from the security and the anonymity of the system. One crypto owner can buy a good from another crypto owner and therefor both benefit from the bitcoin system. There is no need for a new buyer to enter the bitcoin ecosystem.
But "buying" is still investing or bringing economic resources into the system. I am asking HOW holders can benefit within the system? From their holdings? When someone voluntarily entes the system and bring in the economic resources so that the current holder can benefit, that's not benefiting within the system.