The sole difference between a locking and non-locking knife is the blade folding in without any locking/unlocking mechanism. For this comparison i will assume, that you can close the blade with locking mechanism one-handed, otherwise you have an advantage right there.
Short FYI: The (legal) reason is that non-locking knifes can not be used as a stabbing weapon as easily as locking knifes (could be considered a downside in the great outdoors?). Some laws (for example in germany) even disallow folding knifes that can be opened with one hand, as they can be used as a hidden weapon.
Now back to your question. There are no obvious advantages for a blade to not have a lockable blade. But we can get creative! If an accident seriously disables you, closing a non-locking foldable knife with one (impaired?) hand might be easier. Also, when using your knife for batoning (for which you SHOULD use a FIXED blade knife!), the folding blade might put less stress on the pivot, so you don't break the non-existent locking mechanism.
Finally, an anecdotal advantage of normal looking, non-locking, red, classical victorinox knifes: you can take them out of your pocket and use them without having everyone else around you think, that you were up to no good. - As opposed to those tactical folding knifes (which usually lock!). But this is off-topic.
So, you might get creative and find advantages for non-locknig folding knifes, but apart from the fact that their non-existing locking mechanism can't break, there is no real advantage to them, especially in an outdoor situation.