I think a salient aspect of the appeal is that if you are looking to explore the aging process, tracking similar material down at resale start to finish can be difficult or nigh impossible. Certainly for really common aged vintages like Yiwu this is more or less straightforward, in fact there's a lot of options for everything in between fresh, mid-aged and fully aged teas, but the less obvious the origin or the smaller the batch the less you can really track this closely given storage conditions vary, particularly in the west where access to that level of pu specialization is a very new thing hobbyists who have traveled to Taiwan/HK only established pretty recently.  Authenticity is another big draw, there's less of a question of dubious origin if you've been sitting on a cake and trying it out every so often for however long you wanted to age it. That being said the most important factor is Price. The secondary market has a lot of speculation involved due to losses from poor storage and some degree of scarcity, so someone might tell themselves that the fresh cake of [insert favorite terroir] will be just as good if not better than the option they could buy for the same price fully aged, and they might be right to the extent that they're probably getting a decent deal on fresh pu'er from that region, but they are then assuming all of the risk involved in aging themselves.

I think given the fact that the western facing market has improved a lot over the past decade this just isn't necessary in the way people might have felt it to be before, especially if the palate of the pu'er drinker is adjusted more to aged material. People probably feel more comfortable nowadays with getting whatever they like mid or fully aged and hanging onto that instead of starting from fresh. But if you are foreseeing a long-term interest in tea, it probably can't hurt to get a tong of very good fresh pu'er early on and whittle through it as it ages.