Short answer:
For this denizen, the allure is of a bustline greatly in excess of the waistline, which is usually difficult to see "naturally" without an awful lot of good fortune and hard work. Thus, the slim-n-stacked are usually slender girls with aftermarket racks. It's not a preference for the fake tits, it's the overall shape of the silhouette that happens to dictate against natural occurrence. There are some folks with an atavism against obesity, and many of the very-large natural-breasted women don't fall into these people's area of sexual attraction, which happens (there are several threads' worth of flames on this, which I'll not reference here).
That said, given, for instance, two identical 34F/22/35 figures, personality and other attributes being essentially equal, I would prefer the natural bust to the implanted, based on feel, her sensitivity, responsiveness, enjoyment of said bust, etc.
As JoiWest said, there's a mindset among many women who aspire to large bustlines that is aligned with the appreciation of us guys who also like prodigious cleavage - mutual enjoyment, especially in a sexual/sensual area, is an absolute turn-on, at least for me.
So, there you have it. I like your breasts, because, as you said, they're big and perky. You're also intelligent, have a knockout smile, and [insert lengthy list of positive, attractive attributes here], which simply enhances the allure that, for better or worse, was initiated by the attractiveness of your bustline.
Now, before I begin blushing any harder, I'm going to shut the hell up and get some lunch.
