Well they already got profits on their bookstore, why would they need to make a version where you got ads on top of that. I guess if we follow your logic they could build phones, consoles and TVs with ads too. I can understand free books with ads but not the hardware/software that reads it.
Can't believe there is such a thing of having an Ereader with ads. Ok it's cheaper but come on, that really shows us how low they think of us. I can understand for a free product but for something you pay ... like seriously!