The best reasons I can think of are: 1. Combating e-waste. Pack-in cables are convenient but not always needed. 2. It encourages people to buy and use the app

The best reasons I can think of are: 1. Combating e-waste. Pack-in cables are convenient but not always needed. 2. It encourages people to buy and use the appropriate length cable for their needs. With USB-C it's a lot harder to include a 'good for most people' length because the cable connected to the laptop for charging doesn't have to connect directly to the DC adapter.