Aircraft such as the Concorde are extremely expensive to run compared to standard subsonic aircraft, and by virtue of their design can carry far fewer passengers. Even at the time of Concorde's introduction, it was estimated that Concorde tickets would have to be on average 41% more expensive than on other aircraft in order to keep them profitable: http://www.bath.ac.uk/e-journals/jtep/pdf/Volume_V1_No_3_225-239.pdf

To keep Concorde economically viable, airlines had to naturally restrict the extent to which it was available. The aircraft needed to be significantly more full than standard passenger flights, and outside of luxury travel, people were far more inclined to pay less money for a longer flight than to pay the equivalent to first class tickets in return for a shorter flight time, especially given the rise in transatlantic holidays and package deals for families. Following the Paris crash, the airlines realised that the cost of modernising and maintaining the Concorde fleet was not being matched by demand, since people were choosing slower, but cheaper and more comfortable subsonic travel.

For an answer as to why supersonic flight has not made a comeback, try asking on /r/engineering or similar. There are many, specific, technical reasons why faster than sound flight isn't economic today, but the reasons are hardly historical.

In addition supersonic aircraft are far more susceptible to hair cracks due to metal fatigue as a result of higher skin temperature variations than subsonic planes.

Also, supersonic flight is only allowed over sea for non-military aircraft due to the sonic boom. Flying supersonic over land causes a lot of broken windows in urbanised areas. It is no coincidence that the Concorde was only used on transatlantic routes.