Just as we have atheists, agnostics, and theists, we also have unbelievers, fortean, and true believers. Likewise, most of us are steadfast in our belief and are wearing blinders when alternative theories are presented. For those of us willing to indulge, both sides offer some intriguing stuff. True Believers have a vast amount of circumstantial evidence and unsolved phenomena they want answers for. It doesn't help matters much that it is so difficult to get non-biased, intelligent investigation into the matter.
Skeptics have most of their strength in the lack of hard evidence.
They also point out that we still haven't found reason to believe in any life outside our atmosphere.