While I can see the reason for the desire, non-vehicle travel requires stamina, and stamina is used both for sprinting and combat. It'd be too easy to be left open to attack because the system spent the stamina you needed to defend yourself. It's one thing to make the conscious decision to keep sprinting- It's another for an automated system to do it for you.
Beyond that, Enemies can spawn and attack at any time in pretty much any place- Auto-travel would undoubtedly lead a lot of people to get a bad taste in their mouth because they got dead while they were staring at their phone or afk getting a snack. Plus it's too easy to get caught on things in the game world which only ratchets up the danger of any given spawned enemy. There's not really any big long straight lines to take.
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