The cause is the law.

As Livia browsed the bazaar, set high in her sedan, carried by four stout men, her flavor of the month. One a pale and handsome Celt from the far North, one dark and tall African from the far South, an exotic looking, lean male of Seres, and a swarthy, well-muscled Parthian.

Four men for her three holes in the bed chamber, how greedy.

And now they bore her aloft this crowd, sitting on the twin skins of a tiger and a lion. In her robes of Tyrian purple silk and cloth of gold, covered in precious jewels from her diadem to her toes, exposed in her sandals, she had already attracted the crowds attention as she pointed at objects, which her slaves would quickly seize and quicker toss the appropriate bag of coins.

Far too haughty.

But a law had been instituted that Livia neither knew or cared to learn of, but she should have, for your spirit had influenced the Emperor, playing on his own vanity, pride, and fear of usurpation.

Purple silk was to be worn only by the Emperor, and his Praetorian Guard was making its rounds to confiscated every scrap from offending merchants. They didn't even know what they'd do to see someone it, it was too presumptuous to consider.