Why do people bother with hybrid cars?

Hybrid cars such as the Toyota Prius, Honda Civic Hybrid etc. don’t seem to be worth the money to me. I have read that the added weight of thousands of battery banks negates much of the advantages of the fuel efficient engine setup, which means that hybrids such as the Prius and Insight benefit almost entirely from their low drag coefficient body shape.

As well as this, the new generation of direct injection, forced induction engines are similarly economical (for example, the new Ford Fiesta). Hybrids are expensive, and take years to pay off, and are environmentally harmful to dispose of.

Why then, do hybrids sell so well?