1) If you don't show up for the flight, even if you checked in online, you won't get mileage credit.
2) If you don't board for the outbound flight, your return will be cancelled.
3) If you want EQM you have to fly. If you just want miles and don't want them for elite credit, buy flowers, dine out, stay in a hotel, get a credit card, or many of the other ways to earn miles without flying.