There are several reason why writers need other writers. Number one is you can't write in a vacuum. If you take one tip from each writer you meet it moves you that much closer to being an awesome writer.
Writer's groups give you special insight into how your work looks from the outside in. When i write and rewrite and rewrite I miss the simplest things. A good writer's group will tag these things and offer suggestions to improve. I had a great writers group at one time but it dissolved when Barnes & Nobel kicked all their groups out. In protest I don't shop at B & N anymore. I'm an Amazon girl now. I think removing the chairs and groups was a big mistake on their part. I belonged at several groups in our local store and they just stopped all of them and removed those cozy little seating arrangements. Pity. I never left a group without buying something on the way out. Now that I'm not there for my group, I shop on Amazon. My bank account is grateful but I miss my group. One of the members was an agent and she was awesome with the grammar and punctuation. Another was a multi published author who gave amazing critique. Miss those peeps.
I need other writers for insight into the publishing biz. Its changing. Agents used to be the gatekeepers to the world where only the ubber talented and lucky (yes, i think some are just lucky) get passed onto the major publishing houses. Now with Amazon cracking the lock down on the publishing biz its a whole new world for publishing. Other writers are a wealth of information on the in and outs of this new world.
I need other writers for inspiration. Every time I hear about the success of one of my writer friends it inspires me to work harder. I rejoice for every book they publish, every bridge they cross and every moment they shine in the author spotlight. These amazing writers, who forge ahead in conventional publishing or the new world of Kindle and Nook, give me hope.