These accounts are often "cracked" or abandoned. They are frequently banned by Riot Games for suspicious activity or reclaimed by their original owners.
While these lists are popular for players seeking "smurf" accounts or high-level starts, it is important to be aware of the security risks and platform rules associated with them. Content Overview: 1,500 Free EUW Accounts (.txt)
Instead of risking your PC's security with unverified lists, you can: