When I've lived in mobile homes, I've found them to be substandard in various ways. One might be prepared to accept that in exchange for their advantages, but if not it seems perfectly rational to seek other solutions with different trade-offs. E.g., most mobile homes are over 70' long, while tiny houses are much shorter.
The social taboo had nothing to do with quality and everything to do with the mobile home = trailer trash stereotype.
Tiny houses are what happens when a garden shed has sex with a travel trailer. Practically tiny houses copy the floor-plan and interior design of an existing high end travel trailer and paste it into a traditionally constructed building. The result is basically a travel trailer optimized for staying instead of going.
As people realize they want more space than a tiny home they're gonna basically build mobile homes, realize they're heavy as all hell and not really mobile and see that the mobile home people are actually on to something.
It is true that is it partly about class and stereotypes, but the Tiny House people have thought about this much more than you seem to think (I'm currently designing one). Here are some counterpoints.
Beyond class, the other major reason for Tiny Houses appearance is acceptance in local communities. If they look nice, people and the law tend to leave them alone. Also it is nice to be nice for appearances sake.
Because they don't move that much they often get wide permits and skirt the trailer or put it onto a pad such that it appears to be a small house rather than a something on a trailer.
I should say also this perception that Tiny Houses are, well, Tiny, is not quite accurate.
Some of them are very small, 200 sq ft. Many of the new builds for living full time are easily 500 sq ft if you include the loft space.
In America that may be still very small but in many countries such as mine, that is actually larger than many townhouses most people live in.
As for later discovering that they need more space, that is not something that scares Tiny House people. They already built a small house, constructing other modules to do other things doesn't scare them much.
It is difficult to overstate how much less expensive they are than the traditional housing route. 50% of the cost of building in the West is paperwork. That is half off the most expensive item most people buy in their lives.
The main hiccup is about Land. This is solved in different ways, I intend to buy mine.
Most Tiny Housers spend money on quality materials. I've worked in construction before and know that most 'modern' builds won't last much longer than a 30 year mortgage due to cutting corners, substandard materials and an overall lack of attention to detail. I fully expect my TH to last at least 50 years, probably longer, be constructed from state of the art materials, and still be 1/4 of the cost of the average house in my area (excluding land).
Of course not everybody can go this route but it beats being homeless or paying a mortgage for decades. Besides, as a geek it is fun to find out how things work, it is an education.
The point I clearly made is that social taboo is not the only reason why one might prefer a tiny house or indeed any other sort of house over a mobile home. You might not care about the other reasons, but they exist nonetheless.
When I've lived in mobile homes, I've found them to be substandard in various ways. One might be prepared to accept that in exchange for their advantages, but if not it seems perfectly rational to seek other solutions with different trade-offs. E.g., most mobile homes are over 70' long, while tiny houses are much shorter.