I am a big loose tea drinker (teasnob). I would echo a lot of what Pierce said.
I buy loose tea from Upton Teas here in MA, but any loose tea store or mail-order facility can get you good tea.
There is a big difference in taste and, cost to the manufacturer, between most of the teas used for flavored blends and unadulterated loose tea. This even more pronounced with most supermarket teabags. I can not successfully make tea with a Lipton teabag that comes close enough to being flavorful without being bitter. Good loose tea is very flavorful and I drink it straight except for some of the darker Indian teas which seem to work well with a little milk and sugar.
I personally enjoy various oolongs and green teas, I generally do not enjoy the smoky teas and I like several flavored teas. I like earl grey and the other bergamot flavored teas, I enjoy mint teas, as long as there is more tea than mint flavor, and I really like a good jasmine tea. To get a good flavored tea you need to spend more to get a good base tea underneath the adjunct.
It costs me about $7-$10 for 100 grams of good quality tea which produces around 30 servings for me.
So why drink good loose tea?
It is fairly inexpensive.
It tastes great.
It has moderate caffeine.
It has no fat or calories if you do not add anything.
It has many healthy properties compared to other foods and beverages.
Why should you not drink loose tea (with humor)?
Some people can have no caffeine at all.
It can darken your teeth after time.
People will label you a tea-snob.
It can turn into a hobby that is almost as geeky as RPGs.