Straight-8 engines have perfect primary and secondary balance, this allows them to run very smooth. Unfortunately, a straight-8 is a very long engine, and therefore straight-8 engines are not common in automobiles.
Most straight-8 engines were used pre-World War II in expensive luxury and performance vehicles. Bugattis commonly used a straight-8 engine. Postwar, the main users of the straight-8 were American luxury cars belonging to Chrysler and General Motors owned marques, but the straight-8 lost favor by the 1950s, almost universally replaced by the V8. Ford never adopted the straight-8, using V8 or V12 engines from the 1930s on.
See also: straight engine