If someday models like the Piaggio Ape were considered an affordable option for light transport, either commercial or private, in a ruined Europe after World War II, nowadays the market has been more restricted. Almost nobody considers the possibilities of a 3-wheel vehicle as a personal commuter to face the narrow streets in some European cities with their very ancient urban scenario, or crowded Manhattan with its traffic jams. However, these curious vehicles can meet the needs of a wide range of customers, from the European teenager that is not allowed to drive a regular automobile legally (and doesn't like those "qualified quadricycles") but want more comfort and safety than an average moped to the small businessman intending to have a vehicle that arranges the capacity of an average car-based commercial vehicle with the running cost of a motorcycle.
Is not hard to find models closer in size to a Smart offering a cargo room similar to an average economy car-based van. In some cases, the ease to find engine tuning components for some 50cc tricycles is perceived by some young customers as an advantage over some "quadricycles" with their small stationary engines with limited performance parts avaliability. And it's easier to find space to accomodate a snowboard or a skate...
When there is almost no tricycles serving as taxi in the so-called "developed" world anymore, except for a few touristic places, these vehicles could actually be a good option to meet the even-more restrictive environmental laws getting enforced. Due to the lower weight, smaller engines can work properly, increasing even more the efficiency, and the pavement suffers a lesser damage than would happen with a regular-sized taxi. Also, there is one tyre less to be discarded. Another advantage to be considered by some drivers is the cockpit placed in a way that can ease the adaptation of a physical barrier to protect from eventually aggressive passengers, currently mandatory in some cities like London or New York.
For light cargo transport, by the other side, tricycles are still seen as a reasonable option, either in "developed" or "underdeveloped" countries. Even in some countries where a "tricycle culture" doesn't exist, such as Brazil, converted motorcycles have becoming more usual to see, from small towns to main cities.
At last, but not at least, tricycles can be fun to ride...
