Well it depends, really. A lot of people love to think that if you're a grappler, you've won the fight against a striker, even before it has begun.
A skilled striker can keep from being taken to the ground, by moving around, swift strikes, and keeping distance. That's a little hard to do, though.
But yeah, even if you're a striker, you should know some basic grappling, so that you could get back on your feet in case you make a mistake. I know in my old Karate class, we learned a lot of basic grappling, even a takedown.