> We show that the vast majority of Bitcoin transactions between real entities are for trading and speculative purposes. Starting from 2015, 75% of the real bitcoin volume has been linked to exchanges or exchange-like entities such as on-line wallets, OTC desks, and large institutional traders.
So 75% of the transactions are just speculative trading, not transactions for goods or services, which is what is being discussed. Taking the paper's numbers at face value, as a percentage of non-speculative transactions, illicit transactions are 12%, which is quite high.
There are also papers which quantify the amount of illegal activity as high as 46% [1] in 2018.
Illicit activity is still probably the most durable use non-investment use-case for Bitcoin, and realistically will be the most enduring use case going forward.
1. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3102645