Minimum vehicle class for taxi
Taxis are often middle-class vehicles, usually having air-conditioning, leather seats and other amenities. Most often evokes car brand associated with the taxi is a Mercedes, because it is regarded as the most reliable car manufacturer.
A taxi must be comfortable - so middle class or high. I can not imagine that a taxi could be a car hatchback or van. The air conditioning is absolutely essential, especially on hot days, which is recently more and more. As for the leather seats they are easy to clean and disinfect, and the cleanliness of the taxi is as important as comfort.
Quote form Wikipedia about Hackney carriage
The Beardmore was an alternative taxi design used in London during the 1960s and 1970s
Until the late 1950s, vehicles licensed as London taxis were required to be provided with an open-access luggage platform in place of the front passenger seat found on other passenger cars (including taxis licensed for use in other British cities).
A hackney or hackney carriage (also called a cab, black cab, hack or London taxi) is a carriage or automobile for hire. A hackney of a more expensive or high class was called a remise.
Luxury taxi services
Taxis are very useful if you live in the city. How many times a month you happen to use the services of taxi transport? I suspect that at least several times a month, and many people use these services couple times a week.
It is worth considering why choose a Taxi- yet we have buses and metro. What makes the taxi is more convenient and better in some situations? I think it is a matter of getting on to it when and where you want and that you get exactly to the indicated address. This is luxury that you won't get in public transport.