Fresh Turkey vs. Deli Turkey

Exhibit A, Fresh Turkey Breast:

http://tinyurl.com/23b9m7

Exhibit B, Deli Turkey:

http://tinyurl.com/4vaqwy

(Or, as an extreme example:)

http://tinyurl.com/4w6ws2

1. How did product A become product B?  What is the process? I have
heard it referred to as "pressed," but I'm not sure what that means.
Is the main benefit of transforming fresh turkey into a rubbery,
flavorless white blob that it can be sliced more thinly? Or does it
have something to do with making it last longer, i.e., preserving it?

2. Do people prefer B over A? I have always found the deli stuff to be
not even vaguely reminiscent of real turkey.