Ah, Mike Mezack.
See, Alvaro, you don't understand. These are the Proof 70 issues, directly from the mint. These are certified, certified as flawless, PR70; flawless by (PCGS/NGC/ANACS). These coins are not available, let me repeat that, not available to the general public. These are the Proof 70 coins. Now, you will see a lot of other networks offering the Proof coins in a 68 or 69 grade, but these aren't those. These are the Proof 70 coins. This is a rare opportunity to obtain the Proof 70 coins so sought after by collectors. And, for a limited time, we will include a red oak box, suitable for storing these rare gems.
Now, how can you resist that?

I think stabbed coins do serve an important purpose and I do occasionally buy stabbed coins (and occasionally crack them out). In terms of authenticity and a professional opinion of grade, they can be very useful. But, it is important to remember (in the style of Mike Mezack) that buying coins in slabs does not relieve the collector - let me repeat, does not relieve the collector - from knowing how to authenticate and grade coins on some level.
And I do think too much weight is given to the exact grade assigned by the
TPG's. Is it a 69 or a 70? Who knows? Who cares, really? If you are just collecting slabs based on the writing on the slab, I guess that is fine, but I think most collectors focus on the coin in the slab, or a raw coin, and say "that's a beautiful coin".
If you are a coin collector, I think slabs play a role in the collecting market. But if you are just collecting slabs to avoid the need to become knowledgable about the coins in them, I think you are setting yourself up for disappointment someday.