May I add that Maurice Smith trains at the Lion's Den with Ken Shamrock to learn grappling, and has spent time on the ground in the Gracie-style at other schools as well.
I say this not to argue, I love striking arts too, but it is only recently that the strikers like Maurice have started learning groundfighting to stay OFF the ground. Maurice has used his ground skills every time he gets caught...to get back up!
I believe in the high-impact arts, but I train heavily in Gracie Jiu Jitsu and have for years just in case I get taken down.
It is wise to learn both...