Idling the vehicle puts pressure on the modern gas shot systems in today's vehicles. Idling was used in cold or hot climates when gas injection had not been common in older autos. To keep the engine from stalling, individuals utilized to keep it running or it may not activate.
However today, you don't need to do that! The idling you do on today's vehicle burns valuable gas and also leaves fuel residue on the cyndrical tube walls that stay with it because the cyndrical tubes aren't relocating as fast as they typically do. This pollutes the engine oil with carbon deposit and makes your vehicle's innards unclean.