Here are some of the benefits, beyond money, they can have for you.
Experience on boards. VC partners sit on boards--lots of them. If you wonder what a successful VC's calendar looks like, take each investment and multiply by four for quarterly meetings. Triple that for two travel days on each end, and pretty quickly you get to 200 days a year out of the office.
Sitting on boards is not just a means for investors to monitor their investments; it's also a formal platform from which to offer expertise and value without interfering in day-to-day operations. Plus, the fact that investors are involved with so many companies means they bring ample experience. When it comes to board/management relations, they have seen it all.
Help with fundraising. Your existing investors want to see upticks in valuation. It can be amazing to watch them shift from skeptics to salespeople once they have skin in the game.
When it comes time to raise funds for your next round, your VC can be your best advocate. In fact, chances are that your investors have been profiling other VC firms to form an investment syndicate all along. Don't hesitate to lean on your investors for introductions to those other firms.