It can help you get hired, move up in your profession, and show dedication to your chosen career path. It can be a catalyst for cohesion within a PM infrastructure or project management office (PMO). It can give everyone a common language to use. It can show your project clients that the organization is dedicated to real success because your project managers are certified and ready to succeed on the projects they are managing for them.
While this is great – and I would never stand in the way of anyone's certification aspirations... in fact I've helped hundreds follow that path already – it isn't likely how you're going to manage projects in the real world. I've been managing projects since shortly after the first PMP certification testing took place in October 1984. But in every organization I've been in and worked with PMP processes and concepts weren't the norm or of any major importance – project success and customer satisfaction has been the emphasis and that isn't likely to change. PMP is great to have, but it's like algebra... you might not actually use the knowledge very much in real life. It may get you a $20k raise or a better job elsewhere earning more... no doubt about that. But usage will likely be minimal. It's more of a paper and resume thing.