Why Do People Have Different Blood Groups?

Because we do everyone has different blood groups its in are DNA and in are jeans, hope this helped

People have different blood types due to the proteins that exist on the red blood cells. The blood cells themselves are exactly the same from group to group, its just the antigens present on the red blood cells, and the antibodies present in the blood plasma which make the groups different.
 
The blood type you have depends on your DNA, which depends on where you come from. Different areas around the world have different ratios of blood groups...