Webinars - why do we have them?

At WSO2 we started doing Webinars about two years back. We've been conducting them at least once a month since then and sometimes even more frequently. We get valuable information about who really is interested in our stuff by the people who register and attend.
Attendance is usually anywhere between 30-50% of all those who register. A lot really depends on the Webinar hosting system used to present the content. Hosting systems are a dime a dozen and each have their own pros and cons. The main thing I look for is getting good reports, ease of setting up and running and of course it works on any OS. I'm yet to find a system that gives me all three completely. There has always been some give and take.
So anyways the main point of this post however is, what do we really gain by conducting webinars and why should we continue to do them? Yes its a great tool to present our products in a low cost, geography neutral and hassle-free way. As in you can sit at home in your PJs and present all the great things about your products to a whole bunch of people located all over the world! But when it comes to marketing lead generation I'm still undecided on how effective it is.
Other than building awareness can we really expect a person to buy something right away once they've attended a webinar? perhaps the content needs to be geared towards selling rather than just informing? I guess time will only tell as we embark on a new series of product specific webinars this quarter.