Why can’t we feel atmospheric pressure?

The Earth’s atmosphere is bearing down on all of us with a pressure at sea level equivalent to around 10 tonnes of weight per square metre. So simply standing upright means carrying the weight of a small car. The reason we can’t feel it is that the air within our bodies (in our lungs and stomachs, for example) is exerting the same pressure outwards, so there’s no pressure difference and no need for us to exert any effort.