Also, you're usually just drinking the bits that readily dissolve in water, not the whole leaf.

Go to a tea shop and order some Dragonwell, and drink it. Then have a bowl of matcha. You will feel the difference, and it can be a rather alarming one.

Edit: Why that's a big distinction: Your body typically flushes water soluble chemicals fairly easily. It has a harder time with the ones that aren't water soluble, so they tend to accumulate over time. So capsule of tea leaves is probably not the same thing as a cup of tea, from a pharmacological perspective, and theres good basis to assume that it has a lot more ability to hurt you. The same goes for pill version of traditional medicinal teas (echinacea, kava kava, etc.)