Most of the popular ptc websites spend a ton of money in advertising as much as possible whose return they get by large CPC margins for advertisers and users. We have a super low CPC margin which leaves us with only enough profit to keep operating the website. Moreover we are still a bit new and not everyone knows about us, the popularity is increasing and you can feel free to advertise with us and see the results for yourself. 
(Alexa ranks can be improved by fake traffic as well, so it should not be a big factor to compare websites.  )