What is the difference in CD transports?

This may sound stupid, but what makes one transport better than another? I have an old Theta Data Basic transport that I'm using with a Musical Fidelity Tri-Vista DAC 21. The DAC made a world of difference compared to my Theta Gen. III or Conrad-Johnson D/A-3. I can understand that because we're dealing with newer technology, faster and more powerful computers, better decoding chips, etc. A transport however, simply has to read the 0's and 1's, or pits. A CD reader in a computer costs practically nothing and reads fine (I assume), so why should a reader that costs almost $2000.00 be less than spectacular at reading and interpretting data correctly? When Theta tells me that the Data Basic II gives a wider soundstage and deeper bass, why would it? When I hear the Theta Jade is even better, what makes it better? I guess what I'm asking is "Is there a difference, and if there is, what transports are there that will feed my MF Tri-Vista DAC 21 more and better data?" Thanks, this is just puzzling!