I would argue that someone who owns a landrover and goes green laneing has a sports car. and someone who has a lotus seven that only gets used for commuting does not!
Untill the 70‘s a sports car did not mean it was “fast“ just generally lighter. since then it usually only refers to fast cars.
Here are some interesting facts and figures;
1.8 TDCI Ford Focus 1375kg 113hp 207ft/lb 0-60 10.8 118 mph max 50mpg
2.0 ohc sierra 1118kg 109 hp 128ft/lb 0-60 9.7 116mph max 25mpg
Xr3i 900kg 94hp 97ft/lb 0-60 9.7 113 mph max 30 mpg
none are true sports cars but most folks would think the xr3 is even though its not the quickest.