The big advantage of having a lawyer help you prepare a will is peace of mind. Wills are fairly complex legal documents that have tremendous legal significance. After a person dies, there is no opportunity to redo a poorly drafted or improperly witnessed will. While you will not be around to feel the consequences of a poorly prepared will, your loved ones will be left behind to deal with the mistakes which may cause them severe stress and extreme financial loss.
Having a lawyer help with the writing of a will reduces the likelihood that your executor(s) will have to face legal challenges to the will. As well, when a lawyer assists with the preparation of a will, the content of your will is more likely to adequately provide for your beneficiaries.