Why are Newman Projections drawn with 120 degrees when actually sp3 carbons are 109.5 degrees?

Title says the question, pretty much.

For example, in the Newman projection of ethane, the carbon hydrogen bond angles are $120$ degrees, not $109.5$ degrees, as they actually are in an $\text{sp}^3$ hybridized center. Why is this so, and does it have any effect on the arguments traditionally derived from Newman projections?