Many people will not respond to messages without a point, others on this site are not truly participaters or do not answer mails, still others are not actually online due to some computer glitches.
Getting upset over people not saying hi to you will not help you one bit. I would get to know the people in chat first, and find people in there you enjoy talking to, and start having mail discussions with people. Knowing a person beforehand can be all the difference in the world.
I myself answer every mail I receive unless it is inappropriate or the conversation turns into too much fluff for me to handle. Usually when I receive fluffy mails, I mail them back with an explanation of why things can not be that way and explain ways that they can gain what they are looking for in a different way. For instance working with mental shifting for those who want to shape shift, and working with elemental energies for people who want to manipulate the elements. If a person can do this in a calm, rational way, and actually show the person a different way to be, it helps both, so this is what I do.
Getting discouraged will only make it harder to find good friends on here, and harder to keep them. And some of the people on this site are the best in the world, but you have to sort through the chaf to get to the wheat.