I have never really understood why this is the most often quoted / cited / reblogged line from all of Tolkien’s works. It’s not a terribly deep or insightful line, and it’s often misquoted as “All those who wander are not lost”. At best, I think one has to admit that it’s usually used out of context. Just now I saw it prefaced by “Get outside the box others have placed on you.” I think this is the spirit in which the line is most often quoted, and I think this is unquestionably not what Tolkien meant by it at all.
In The Lord of the Rings, it appears as one line of a poem prophesying the return of the king out of the wilderness, where he and his ancestors for generations have been (thanklessly and anonymously) protecting the edges of the wild, keeping the land safe for those who do not know their danger. Like the other lines of the poem — eg., “All that is gold does not glitter” — it’s a protest against judging by appearances, and an invitation to see hidden value, and I think it’s in this capacity that it is often used today. There’s nothing wrong with that in and of itself. But it misses something crucial: that the line is not just talking about mere wandering. The wandering of Aragorn and the Dúnedain who serve under him serves a purpose, both interior (preparing him to be worthy of the kingship it is his right to take up) and exterior (keeping Eriador free of the Enemy’s influence).
Not that Tolkien would have disapproved of wandering for wandering’s sake. He and his good friend C.S. Lewis often took walking tours of the English countryside on holidays (something I wish would become more of a trend here in America), taking in the beauty of the countryside and taking whatever shelter they could find for the night in inns, farmhouses, etc.
But ultimately, the wandering that Tolkien is really talking about is not wandering for wandering’s sake. His wanderers ultimately have a destination (both in the long term and in the short), and if such was not the case, then the entire point of Tolkien’s poem would be null and void.