Hi, sorry for the late reply.
We have considered it because the site has far more downloads than likes. We asked in some private groups but the idea made some people angry, mostly DJs who download a batch to listen to off-line and don't know if they "like" the track yet.
We compromised and changed it so you at least had to be logged in to download. That way it's easier to click "like" if you're already logged in.
There are maybe other ways to encourage "likes" and happy to hear any suggestions.