Seems this isn't a question related to tubebudd I've moved it to YouTube discussion. I'm not overly sure why it wouldn't show data, Gunjit is pretty much spot on, I just don't know how much data specifically it would need, BUT also be aware that that feature is still in beta and in the process of being rolled out. I assume once it's been fine tuned a bit more it might be able to gather more data. It was at about 50% rollout a few months ago with some channels having access and some not, so I'd guess it will fix it'self up soon enough. I'm not sure how much data it would need, I'm not sure what kind of data it uses, if it means your subscribers who have been watching, or just people who have watched your video in the past.
You could always try asking @teamyoutube on twitter, but my guess is they'll give you the same answer, that it's still being rolled out. There was rumor that it wouldn't even stay around because they're testing it first.