Maybe you should try correcting texts in Spanish, because there are lots of them written by English native speakers. I saw on you profile that you have never corrected something or answered to a question about Spanish. I think these people would enjoy your help/comment/correction and your chance to get a language partner will increase. A few days ago I read a text from an English native speaker, probably from England - he said that he talked to many people, but could not find anyone that is really interested in a language exchange Eng/Spa.
Although I have a very poor English, no photo of me and nothing about me on my profile, I receive a day at least three messages from men (even from English native speakers) and I rarely answer to them. I am not willing to answer to "hi how are you" or "hi let's study english together do you have skype? what's your phone number?". I also do not like to answer messages from people who have just registered (in my experience they never come back) or that have never posted a text or a question or never taken a class.
I think that many people are tired and maybe they get so many messages (most "hi" messages) that they have no will to answer, specially when they write on their profile what they are looking for and not always they are interested in learning the language that the other person has to offer.
Answering to your question -> I take classes because the prices in Italki are much cheaper than private lessons where I live and I have some partners (from the USA and Germany) or people I like to talk with - but I agree that is quite difficult to find someone with interests in common, and time to become a partner.
I have the same impression and am also a little bit disappointed.
Sometimes people just pretend to be interested in the first place, let you talk and then... nothing comes back from them, not even a short message saying: sorry, I don't have the time anymore or just a polite goodby note.
What I also dislike are these flirty messages (hence the profil pic with nothing but a lovely London skyline). Or these short ones like just "Hi". I mean, nothing informative, social or a tiny little story why they are interested in an exchange, how do people expect others to answer to that?
I think one needs time and patience to find the right language partner here.
It's important to create a real win-win situation. If you expect somebody to help you, you yourself have to be willing to do it, too.
Also don't stop looking for a language partner outside the virtual world, if you can. :-)