In the US Kik has a pretty active userbase; but it's demographics skew older, poorer and more female and more rural. So that might be why you haven't heard of it.
Are you sure? This wasn't my impression and what I'm seeing from a quick Google is pretty different on multiple counts:
"Quite surprisingly, close to 70% of Kik’s users are men. It is most popular among young men between ages 20-24. Vine and Flickr are popular among men too, though their users tend to be a little older: 25-29 and 35-39, respectively. Not so surprisingly, Instagram and Pinterest are more popular among women than men. Women also prefer Facebook Messenger over WhatsApp and Kik"
"Quite surprisingly, close to 70% of Kik’s users are men. It is most popular among young men between ages 20-24. Vine and Flickr are popular among men too, though their users tend to be a little older: 25-29 and 35-39, respectively. Not so surprisingly, Instagram and Pinterest are more popular among women than men. Women also prefer Facebook Messenger over WhatsApp and Kik"
http://www.vertoanalytics.com/the-demographics-of-social-med...