This is an interesting question, because this is exactly what some Japanese people ask me when they see a foreigner (me) working in a Japanese tea shop in Japan. Even if they know I'm Japanese Tea Instructor, some ask me "why Japanese tea?". This question shows how almost Japanese people does not consider Japanese as something that is good and deep.
I explain them that Japanese tea is not only Shizuoka and Uji, there is wonderfull teas all around Japan. Also, I explain that there is sencha, gyokuro, kabuse Cha, kamairi Cha, etc, but considering only sencha, there is a lot of sencha types, not only the asamushi-fukamushi distinction, processing method, growing area, tea three cultivars makes thousand and thousand of variations. Recently, more and more new cultivars with great perfumes, almost are still rare, but if you take the time to search, you can find incredible Japanese teas, ie Koju cultivar have a wonderful grape-muscat flavor, .... Again, some adventurous growers try to innovate processing methods, like mister Hiruma.
Sencha is too general word, because in the reality, it is matching with a lot of very different things.
Then, like others teas, brewing methods gives a lot of possibilities even with the same tea.
So, why japanese tea ? Because it's as deep as others teas, there is a great diversity of tastes, flavor, ways to enjoy it, a fascinating history. Unfortunately, its diversity still remain not enough diffused, in the world, and, sadly, in Japan too.
After, everybody have preferences and tastes.