If you're like most people, you probably get more junk email than you know what to do with.
That's a big problem when it becomes hard to sort through all the messages you don't care about to find the really important emails, like those from your lawyer.
When you hire a lawyer, it's because you need help with an issue that you can't handle on your own. When your attorney sends you an email, it's not just to say hi. It's because they either need to tell you about a development in your case or ask you for something they can't get without you.