What do new users experience when they first login to your SaaS? If you're not sure, you should sign up for a trial of your own product, and take a look. See if you're making one of the 3 most common onboarding mistakes.
Why is onboarding important? Well, remember the time you went to a restaurant you hadn't ever been to before, and nobody was there to welcome you? You just kind of stood around, waiting for something to happen. That was uncomfortable, wasn't it? And even though you only waited around for five minutes, it felt like 30. And not knowing what to do during those five minutes (or having anything to help you out) was frustrating.
A hostess greeting you when you walk in is a small thing--really, all she says is "Welcome," "The wait is about 10 minutes," "You can sit over there," "Your table is ready"--but she gives you assurance, and helps you feel more comfortable.
Onboarding new users is kind of like having a hostess at a restaurant. It's a small thing. Maybe all your onboarding does is say, "Welcome," "Here are some options..." and "Here's how to do them..." But having something to tell your new users what's going on can give them assurance, and help them feel more comfortable.