Multiple reasons... History being one. They clear the books after market too, it's a big part of catching the crooks and frauds. Almost certainly makes audi

Multiple reasons... History being one. They clear the books after market too, it's a big part of catching the crooks and frauds. Almost certainly makes auditing easier. Is executing trades quickly bad? Or is flipping an equity quickly bad? I cam see no good that comes from buying and selling in milliseconds; the tax should inversely exponential to the hold time or something.