Are dinosaur eggs really that rare?

Okay, so I have been playing Stardew since it came out on Switch. I've had like 6 farms and every single one I always get at least 4 or 5 dinosaur eggs on my first Skull Cavern run that I do. Same with Prismatic shards. I always see everyone posting and saying "don't donate your first prismatic shard/dinosaur egg" but I always do so anyway. Because my first is usually one of multiple. In my first playthrough I actually got a Prismatic shard from fishing before I even unlocked the Desert. Am I just immensely lucky?