Most repacked games cannot access official Steam servers for multiplayer unless they use specific "online fixes" that simulate a legitimate connection.
Users often look for repacks to fit more games onto smaller SSDs or SD cards. Risks and Safety Steam-Repacks
Repacks are technically a form of software piracy if they distribute copyrighted game files without permission. While some users "buy the game but download the repack" to save bandwidth, the distribution and use of these files often violate EULAs and copyright laws. Most repacked games cannot access official Steam servers
Collectors use repacks to keep "complete editions" of games (including all DLCs) in a compact format for long-term storage. Steam-Repacks