Cost of capital. If you have an expensive cargo load on sea for 80 days port to port, it's a lot cheaper to finance than for 120 or 150 days. Same reason we air-freight some cargo today, rather than sea, even if it's not perishable. Interest rates for this business were also higher than the risk-free rate, and rates were higher overall.

Also if you’re first to market in a period of high demand, you can sell at higher prices than those that come later. See https://www.smithsonianmag.com/history/the-great-tea-race-of...

“But in the middle of the 19th century, demand for fresh tea was such that the first vessel home from Fuzhou or Shanghai could command a premium of at least 10 percent for her wares, and a clipper ship that cost perhaps £12,000 or £15,000 to build might bring home a cargo worth almost £3,000 on her first voyage.“

Yeah, it's like the Beaujolais Nouveau Day rush every year, shipping 8lb/gallon wine by air to get it faster :)

One clever thing they did to prevent the porcelain from breaking was that they used tea for the packaging. Not sure what they generally used in those days as polystyrene foam wasn't available, maybe wood cuttings? But if they can use something that is itself valuable cargo like tea, why not!

High value. Not per Shia or, but John value and rather subject to breakage (so the fewer days it spends at sea presumably the less breakage).