The Rucksack Other Arms from the British army and the Osprey Porter are both “single” compartment backpacks where you can hide the shoulder straps. This allows you to use it as a hand carrying bag. Both the backpacks are not very high compared to their width.
If you spend most of your time carrying your luggage at your back when hiking or going to the woods and mountains, then a real backpack is most suitable. If your backpack spends most of its time in a luggage compartment of a bus, train, air-plane, mini van, taxi etc. then a single compartment bag with no extra straps or side pockets is more suitable. This setup comes close to a suitcase that you carry on your back.