I have to run with the old "Maddog" on that one . The usual reason for fights winding up on the ground is that the protagonists are either 1] drunk 2] not actually any good at fighting standing up 3] Both.
I only wound up on the ground twice in ten years- however, you need to know what to do when you get there! They were both multiple opponent fracas and my first concern was getting back onto my feet so I wouldn't get stomped to death.
As for any grappler will beat any striker- sheer bollocks. Its the individual who wins or loses, not the style. If you want to be "street effective" learn grappling and striking. There are plenty of grapplers who can't strike well, and plenty of strikers who can't grapple. They are all at a disadvantage.