If by don't know by now that you must travel via walking, skateboarding or biking in order to be successful at Pokemon GO, then don't worry, because you'll soon see just how much is necessary to achieve the ultimate goal of catching 'Em All. If you don't walk or use one of these other means of movement, then the game cannot track where you are and the distance you have traveled. And if it can't do this, then you won't catch many Pokemon, you won't gain enough stardust and candy to power up your Pokemon, you won't be able to battle many gyms and raid battles, and, most importantly, you won't be able to find and hatch all those valuable eggs with numerous Pokemon Species. (Unless you dare to hack and risk being banned from playing altogether.)
One must also remember to keep both their phone and the application on while moving, as there is no tracking for the game when either of these aren't. And because of this, your phone will easily begin to have its battery drained, so having a secondary phone to play on or a portable battery charging pack will certainly come in handy. And as the game says, while walking around on the hunt, don't forget to always watch out for your surroundings.