Well i'm not 100% sure how faucets work but I assume the cost people pay to advertise outweighs what they give away, therefore still making a profit.
Faucet earning is very low even with high pageviews. Google ads or other networks does not pay much unless u can have direct advertisers. The reason is that, faucet traffic shows very less conversion in terms of ad spending. Hence faucets should be on last priority to try out for profit.