Plus, even if the blood is maintained at a near neutral pH, that does not mean that the buffering system is not taxed and stressed. Ideally they strive to reduce the large workload of these buffering system.
It really is not a strain on the buffering system unless there is severe alkalosis or acidosis, which are rare instances. Again pH is primarily maintained through respiration. It is not a strain on the body to increase its respiration a little if the blood starts becoming acidic or slows down respiration if the blood becomes too alkaline.
Also keep in mind that the buffer system goes both ways. You can stress the buffer system by trying to force the body in to an alkaline state, which means the body now has to try to raise its acidity. This is especially true of the intestines and stomach when hydroxides and carbonates are ingested. The neutralization of these normally acidic environments requires the body to work much harder to restore those acids. And if the pH of the blood is affected, such as with milk-alkali syndrome, the body has to work harder to get the pH of the blood back down. This is why people should stop trying to force the body in to an alkaline condition. It just ends up creating other health problems and draining the wallet with overhyped and over priced alkalinizing gimmicks.