The future is Bluetooth, not Lightning connectors. Apple made it quite obvious that they want people to move on the wireless however there are many reasons why this MacBook still has it. Many people don't know that the jack serves more purposes for laptops other than it just being used with headphones. Prior to 2014, MacBooks supported optical digital input and output via a hybrid 3.5mm jack (mini TOSLINK), but professionals are moving to more modern equipment with high-bandwidth digital transports like USB. These devices will take a little longer to move on to USB-C or wireless capabilities but it will happen very soon. You can not compare a mobile device with an actual computer that is designed to do such productive work.
The lightning connector is Apple's way of trying to prevent third party chargers and other devices shared with Android that could ruin the integrity of their device. They can switch to Lightning to USB-C in the 8, but it's only a matter of time before they have to go all in on USB-C in their iDevice category to keep up with their Mac future plans.
It's also worth noting that there was no good way of fitting the force touch home button and make the phone fully water resistant with the headphone jack still in it. MacBooks have a lot more space and there is no application for taking it underwater.