Green tea needs shorter steeping times and lower temperatures because it's more delicate than other teas, like black or oolong. Since green tea is minimally oxidized, it keeps its fresh, light, and vegetal flavors, which can get ruined by too much heat or steeping for too long. If overdone, it can become bitter or astringent, which is why careful brewing is important.
Green tea also has more catechins (antioxidants) and L-theanine (an amino acid), both of which are sensitive to heat. Lower temperatures, around 160°F–180°F, help release these beneficial compounds without breaking them down too fast, keeping the flavor balanced and smooth. Plus, green tea’s tannins, which add bitterness, are less likely to be over-extracted with gentler brewing. This way, you get a naturally sweet, delicate flavor without any harshness.