Original back in the eighties BMX flat pedals were all sharks teeth to provide grip like these –
But then Shimano figured out with the original DX flat pedal that having a concave surface gave better grip and feel without massive pins
In the mid nineties DMR resurrected this style with their V12 and concave pedals have been the way forward ever since IMO. I’ve tried pedals with no concavity (spank spike), even convex pedals (Canfield Crampon) and although they feel “okay”, I’ve always gone back to a concave platform. Currently on the new V12’s, a set of Straitline Defactos. and a set of Easton Cullys.