But that's the point with stepping really - most people were like Joshua in that they generally came back to Datum eventually. Maybe Joshua being a natural stepper meant he could stay away longer than usual, but I got the impression that a fair proportion of people treated Long Earth almost as a vacation/long weekend/leisure destination or, like Jansson, as a commute? Which is why it had such an immediate impact on the economy in Datum because people could just go without any restrictions, which is a huge attraction just in itself.
Even out in the 100,000's they still had contact as well - Jansson knew that Tilda had died of cancer but her son didn't because he ignored all their letters. People will look for new, better lives for all kinds of reasons - look at the Vietnamese Boat People or even the economic migrants (assisted passages) to Australia & NZ between the World Wars and in the 1940s/50s. A lot of those people were leaving relatively cushy lifestyles for the chance to own property or be their own bosses etc.
Seen in that light, where anyone who's not phobic can make a stepper and just go, it's not really that huge a risk once it's become a common activity, even though the 'one person per World' pipedream is obviously soon going to be a complete and utter washout on the Low Earths .
If it really was possible and 'everyone' was doing it wouldn't you want to have at least a look...?