Would you like to learn Japanese? Then you are welcome to join my group of friends.
How do you approach Japanese speakers? It is hard to say why some Japanese speakers wouldn't respond to your correspondence as I don't know how you approach them.
Not only Japanese speakers, but I believe some of us are hesitant to engage in immediate friendships. Some forget manner and become rude online as they don't see each other, some might be here to sell us something, some might be here just to gain virtual popularity for some reasons, but many of us are here to learn.
But, we won't know till each one of us prove that we are sincere about learning.
Also, the majoirty of members in italki.com is here for learning languages. If you are just seeking Japanese friends without any interest of learning the language, it might be difficult to gain a friend here.
However, if you are learning Japanese language and would like to receive some advices and willing to help them learn English, I am certain that you will find many friends here.
Wishing you all the best.