Any regular traveller who uses land bordeers will have encountered this problem. If you apply to enter the country yuou need to prove how you are going to leave it. That's fine if you happen to be on two weeks holiday and hold a return ticket. It's probably ok if you have a round the world ticket but if you are a true nomad who wanders from country to country then everything changes. We left home eighteen months ago and have wandered all through South East Asia making landfall in Dawin Australia where we were quizzed about why we were entering from Timor Leste. Luckily the nosy beaurocrat was more interested in why we were leaving a so called war zone than whether we has a ticket to leave Australia so we managed to get in. Travelling in the other direction is not so easy. We're ok to enter the European Union but try a Russian landfall or Indonesia and the same does not apply. Do these people not understand that local buses do not cross boirders and there is a way other than using an aeroplane or a travel agent to mnove between countries with contiguous borders.
We need a discussion here about which borders it is possible to cross without onward travel documents and hoiw it can be done.