You walk into a tea shops and find countless varieties. All those herbal teas: not really tea. They are made from non-tea plants, most of which taste nothing like real tea. Peu-er is probably as close as it gets.
The remaining (real) tea all comes from the same singular specie. Green and black is just a difference in processing of the same plant. White tea is just taking the tips of the tea leaf. All the flavors are just ways we dress it up with additives, or by smoking it (e.g. Russian Earl Gray).
Why the lack of biodiversity? Because no one has genetically modified a tea tree to give us more choice. There are far more tea drinkers in the world than coffee drinkers. That’s ideal b/c coffee has environmental consequences. It also means there should be a huge market for something like a tea tree that is married to a maple tree to give us maple tasting tea, or GMO tea that tastes like coffee.
Camellia sinensis comes in two major natural varieties, C. sinensis v. sinensis and C. sinensis v. assamica. Other natural varieties (that I didn’t even know about before looking into it just now) are v. pubilimba, v. dehungensis, and v. madoensis. The related species Camelliia taliensis is also used to make tea, especially pu-erh.
In addition to these natural varieties, there is a huge variety of cultivars. And the terroir makes a difference. But I think that tea drinkers by and large like their tea to taste like tea.
tl;dr Camellia sinensis has both natural and bred varietals.