The environmental weenies have determined that zinc in motor oils is bad. Zinc is an anti-scuff, pressure additive that older engines need to stay healthy. Since most, of not all newer cars have gone to roller cams, the necessity for zinc has gone down. Rotella, EOS, and other additives replenish the zinc, and strengthen the lubricating film of oil.
Many run flat tappet cams (stock style) without a lot of drama. When I went thru my engine, I decided to go with a roller cam, because I didn't want to relive the adventures of others going thru a proper break-in, and having the cam go flat a month later.