Well the major difference is that optical drives were becoming more and more obsolete with the increase in streaming and download services. With spotify, netflix, amazon prime, itunes, etc, the main uses of optical drives for dvds and music disks were decreasing in popularity pretty rapidly. The only uses I ever have these days for my optical drive is to install drivers for new hardware in my PC, which in most cases can be found online anyway. And even this isn't needed on Macs because, unlike customisable PCs, you'll never need to install drivers for a fancy new PCIE wifi card.
The headphone jack is different, because it isn't being replaced by convenient online services. Sure there are wireless alternatives, but the cost increases, difficulty of pairing, and the fact that 3.5mm is a standard across a huge range of devices from simple headphones to complex audio recording/mixing/playback setups means it just cannot be replaced. They could remove the optical drive without including the external drive because most people wouldn't need it, they definitely could not have removed the headphone jack without including an adapter in the box because of how popular the jack still is.