These wind chill and “feels like” numbers actually serve an important purpose, not simply for narcissistic, “making it sound worse than it is” purposes. These temperatures give an equivalent for how the human body will react. On the cold side, the wind makes the body more susceptible to frostbite and other related dangers. If it’s -10 but windy enough to have wind chill of -25, this is indicating that exposed skin will be at risk of frostbite much faster, in the same amount of time as if the temperature was -25 with no wind. This is important so that people dress appropriately when outside; if they only dress for -10 they could be seriously injured. Similarly on the warm side, a heat index is driven by humidity. High humidity makes sweat less effective at cooling the body, so people outside have a higher risk of heat stroke or other potentially life-threatening conditions.
On both ends of the scale these numbers are meant to help people who will be outdoors to take appropriate precautions. It’s of little importance for people who will only be outside a few minutes as they move from a vehicle to a building, but for those who must be outside for long periods (such as for work) these numbers can help them take precautions against serious or even life-threatening injuries.