Why do rock type attacks rarely have 100% accuracy?

Question

The only Rock Type attacks with 100% accuracy are Ancient Power, power gem, smack down, and accelerock. Why is this?

Comments

I think power gem, diamond storm, and accelerock have 100% accuracy. Maybe it's because it's hard to hit things when throwing rocks, or maybe it's because Game Freak logic.

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Diamond Storm has 95% accuracy I thought....

Yup it does.

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Game Freak logic questions occasionally get good answers. This one didn't, but that doesn't mean we should close it.

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Ancient power does not have 100% accuracy

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https://bulbapedia.bulbagarden.net/wiki/Ancient_Power_(move)

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It's not that rare for rock attacks to be 100% accurate.

/nms rock, acc=100:
Accelerock, Ancient Power, Hidden Power Rock, Mighty Cleave, Power Gem, Salt Cure, Smack Down, Tar Shot

this makes up 32% of all rock moves (8/25), as opposed to another type... say, electric, 53.3 percent are 100% accurate, it's 46.6. Really not that different, although noticeable

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@Frog note that Accelerock, Mighty Cleave, Salt Cure, and Tar Shot are currently signature moves (and Tar Shot is a status move anyways). Barring Tera Blast, Smack Down is the *only* 100% accurate physical Rock move that's been distributed to multiple Pokemon. This is a design choice replicated by no other type.
Even if the raw percentage of 100% accurate moves isn't dissimilar to other types, it isn't perceived that way—most of these moves are either signatures or irrelevant competitively.

Answer 1

No one knows except Game Freak. But my speculation is that rocks can be dodged more easily than other attacks. Simply throwing a rock at an opponent is less likely to hit than, say, engulfing them in fire.

Hope I helped!