Lawyers rarely have creative influence on the game itself. But they still fulfill two important jobs in the game industry.
The first is intellectual property (IP) law. Games and all their individual assets are IP which is protected by copyrights, trademarks and sometimes patents. Lawyers are required to advise development teams how to not violate the IP of others and how to prevent others from violating their IP. And keep in mind that games are almost always sold internationally nowadays, which means that an IP lawyer worth her money should not just know about the IP law in the state she is licensed in but also have a vague idea about how IP laws differ around the world.
The second is contract law. Game developers often don't just work with regular employees (employment law is a whole legal can of worms in itself, but usually one which legal laypeople can navigate on their own thanks to plenty of literature). The game industry does a lot of freelance contracting, which requires non-standard contracts. Especially considering that game developers sometimes form agreements which are unusual in other industries, like work-for-work or revenue share. Those contracts need to be complicated and non-standard to cover all possible situations, which makes it important to consult contract lawyers.