Heat Index and Wind Chill

how come thermometers (like the ones at banks) cant’ detect heat index and wind chill? is it just because we have sweat and oils and stuff on us that evaporate and they don’t? and how do meteorologists measure heat index and wind chill if a regular thermometer can’t detect it? do they have some kind of special device or just a formula using wind speed, humidity, temperature, etc.?

I am not a meteorologist, but this is my understanding:

Temperature, humidity, and wind measurement each require separate instruments. Bank displays, evidently, have just one. And the heat or wind-chill indices are calculated as “equivalent” (or, “how it feels to you”) temperatures based on a temp + humidity (heat index) or temp + wind (wind-chill).

From The Handy Weather Answer Book (Walter A Lyons, ©1997), on wind chill (pp. 205-206):

And on heat index (p. 241):

If you wanted to spend the bucks, you can actually get your own hand-held weather station that tells you all that info.