I was out at IMI in the first year I had my first street bike. It can be scary, and if someone doesn't want to go that route, then there's no reason to push it. It's not for everyone, it can be expensive, but it does let you get to know your bike and what it can do a lot more than any type of (safe) street riding will. Even if you aren't fast, you'll still learn a lot by just having to concentrate on your riding, and not wondering if grandma is about to turn left in front of you, or if there's gravel on the road around the next corner.
I know it helped me a lot getting out there, even if I wasn't going fast. But it isn't for everyone for sure.