quantify "a lot of people" sign up without knowing its illegal? no i cant quantify that, its based on discussions i've had in the past with people who used dodgy fire sticks and were persuaded they were kosher by the people selling the services. Mostly older generations, My parents mates levels. they were actively pusuaded by the people selling them that they were on the up and up.
I knew plenty of people who bought R4 cartridges back in the day for Nintendo DS/3DS levels who had no clue the were breaking the law downloading games. again mostly in the boom where DS's moved into the non gamer market.
I know about 15 who have had letters from ISP's. 2 have been fined. however if thats a fine by Police or a fine by "we're are lawyers for film company x, we know you have downloaded y, pay up or we prosecute" is not something i know.