Can you write your own will? Of course you can. There's no law that says you can't. There are wonderful websites, nowadays, like Rocket-Lawyer and LegalZoom, that will walk you through the process and let you print out a document that, if you get it signed in front of 2 witnesses and a notary, will work just fine.
The idea that it is a threat to my profession if people can do their own documents is absurd. If you know what you need to do, quit procrastinating and go do it.
So what do you need me for? When you don't know what you need to do. When you know that something should be done to make it possible for your children to take care of you if you fall ill, but you are not sure quite what. When you have a wayward or disabled child, and you are not quite sure how to provide for that person. When you want to protect yourself and your family from the American Nightmare that is long-term care in this country, but you don't know how.
When you need guidance. When you need legal counsel. That's when you need a counseling lawyer.