Whether solar is economically reasonable is a matter of the variables of your location. You need strong retail power parity laws, for example. If solar makes sense for one person it makes sense for the other people in the area. Why does there have to be a “catching on” effect?

Theoretically, if solar did not make much economic sense at all, it would be purely a signalling thing. And those kind of things do spread by the ”catching on” effect. People might then get solar panels just to be seen as the kind of people who have solar panels, i.e. not the wrong kind of people.