I think that part of her attempt to replicate the success of TSP in subsequent books is that she has to find a way of making them look hapless, victim-y and a bit on the back foot/down on their luck.
The fact is that TSP has made them rich, leisured people with ample time to take off and walk because they don’t need jobs, essentially makes them the people they claimed to pretend to be in TSP. Moneyed retirees with no responsibilities who can afford to walk LD trails at their leisure for fun.
Objectively, the walk in TWS is an expensive holiday in a famously expensive country with friends, so SW has to make pious noises about thank heavens they don’t have to pitch a tent on the grass under the airport flight path, patching her old rucksack, and poor old Moth struggling and losing a tooth in his Mars Bar to stop us noticing that they take an international flight and stay in a hotel to do this walk. It’s not two homeless people semi-starving in a tent, it’s two comfortably-off people going on holiday to walk a tourist path.
Again, the walk in LL is a four-month holiday which involves a car collection service, numerous hotels and taxis, buying bicycles for one stint and posting them home, ordering kit online from their smartphones for delivery to a hotel etc etc. To stop us noticing this, there’s all that guff about Moth’s deterioration, ill-fitting boots, rain, Dave worrying that Moth’s too ill for the walk, and Scottish people not serving them inside cafes because they’re not locals etc.
It’s what SA put his finger on in the NS piece, really. That he gave his blessing to the use of his name in TSP largely because they sounded poor and desperate. But that he was less inclined to be lenient with them rearranging his career timeline for laughs by the time TSP had become a glossy, best-selling, award-winning phenomenon being adapted for film. This couple are definitely no longer ‘down on their luck’. It’s just that they’re trying to stop us noticing because the ‘brand’ is ‘stoical, relatable, child of nature victims’.