Where are your sources that they do travel?

i've never seen a study concerning the movements of frogs and toads except during breeding migrations. Those were personal observations, along with other observations from other people and a few books.

I'm not saying enclosure size doesn't matter, I'm just saying that I (and many other people) have kept adult grays in ten gallon vivariums with virtually no problems. If you want to project yourself onto a frog (which is, frankly, an unintelligent and extremely apathetic animal) and give it a super sized enclosure so it will be "happier", go ahead but don't try to discourage other people from keeping them by pushing your unfounded opinion.