Blogs bring fantastic value to your site, and the ability to sell your product / methodology / sense of who you are.
As mentioned above, if you can't write it yourself then get someone else to. Though to be honest, look at it as an opportunity to map out in more than just 140 characters who you are and what you do.
Sites without a blog almost seem to be avoiding giving the visitor a means to get a more human sense of who you are and what you do. You don't need to 'overshare' details about your personal life, but anything that gives more than just the slick PR version of your company actually helps to convince potential customers that you're not a faceless, unresponsive organisation.
Naturally I am a little biased because we help people to develop and roll out their content publishing schedule. But if you can create interesting, readable, and share-able content, then you are offering the world, and google search algorithms more reasons to come across who you are and the great things you are doing.