Most modern commercial aircraft (e.g. 737, 767, 777, 787, 747-8, A380, etc.) feature inboard nacelle chines to improve flow over the upper surface of the wing at high angles of attack. However, many other similarly purposed aircraft (e.g. DC-8, L-1011, 757, 747-400) do not have nacelle chines. If these chines are so critical for optimum takeoff and landing performance, how are so many planes able to function just fine without them?
The chines help when the nacelle is very close to the wing. When the engine of Boeing's 737 was changed from the slim JT-8D to the higher bypass ratio CFM-56 on the 737-300 and later, the chines were essential to avoid large flow separation. Generally, aircraft with higher landing gear can afford to have more space between nacelle and wing and do not need fixes like chines. But when a new engine has been fitted to an existing design, chances are that some vortex generators are needed to fix the new flow conditions.
For the nitpickers: The 737-100 and 200 had underslung nacelles which left no space between wing and nacelle, but that is aerodynamically similar to a nacelle at a larger distance, because no narrow flow paths are created which produce steep pressure gradients. Only a closely mounted, but still separate nacelle will have these flow conditions which need to be remedied by energizing the boundary layer.