• If you're not communicating, you're not serving your clients well. I don't care how good you are at what you do.
• If you're not communicating, your clients don't feel comfortable.
• If you're not communicating, you come off as unreliable. I don't care if you DO meet the deadline, if I don't hear from you until 2 minutes before something is due, it reflects negatively on your performance.
• If you're not communicating, I don't care how good you are.
• If you're not communicating, your expertise and knowledge is forgettable.
I would rather hire someone to do a job that will reply to an email within 8 hours, but costs twice as much—ok, maybe not twice as much, but you get the idea.
Here's the bottom line. There is a chain of command here, that you may not at first see, but a lot of times, our goal is to make our clients look good to their bosses. And that goes down the line. If I hire a contractor to do work for me, but I can't get them on the phone, they miss deadlines, they don't tell me when they are overloaded, etc. I end up looking bad to my clients, because they start looking bad to their clients (their bosses).
Clients remember. Their bosses remember. Communicate. It makes you more than simply desirable to your clients. It makes you valuable.