Disclaimer: I do not own Steven Universe.
Flaws are not acceptable in gem society.
They make a gem imperfect. Imperfection is frowned upon. Flawed gems are to be destroyed upon discovery. It doesn't matter what type of gem. Pearl. Peridot. Ruby. Saphire. Quartz. Diamond.
Flaws are defects. Defects are not,can not and will not, be tolerated.
Of course, that doesn't stop some of the higher ranking,and more eccentric gems. Take Rose Quartz and her Pearl for example. Pearls are common. They have very little practical use. Rose saw a defect and made it into something important. Something defining.
Instead of a defect, it was an indicator of rarity.
Rarity is praised among gem kind.
Diamonds are the rarest among gem kind. They rank the highest. They are viewed as perfection. It's only natural they would take Rose Quartz lead on the matter- even after she rebelled.
Of course, the Diamonds couldn't have anyone thinking they sympathized with defective gems. They chose minor defects. One's so minor one would have to spend every waking moment with a Pearl to notice them. Personality defects that made the pearls more effective.
Take Yellow Diamonds Pearl. She is harsh. She is cruel and very much snide. If she can get away with being rude she will.
It's part of her defect.
Part of what makes her rare.
Gem kind prizes rarity above all else.