I completed my full set in binder last year, and I have quite a few no rarity cards graded in PSA 9 & 10. No rarity is not rare in itself, but it becomes quite rare when you’re looking for an NM-Mint state, which makes it quite difficult to obtain PSA 10, and it can sometimes be easier to crack a strong PSA 9 to try for 10.
Another important point is that holographic cards are not the rarest to obtain, but for me, rare cards of the series are the hardest to get (Dragonair, Electrode, Electabuzz, ect…) especially in NM-Mint condition, which is very, very hard to get (as can be seen from the price of PSA 9 and 10 even more so).