WHAT DO ALIENS WANT?
First, they want to study our world and its various lifeforms, geology, etc. They want data – they want to know what they’re dealing with. At some point their political leadership structure (which may be skewed in favor of science or commerce) would make the cost-benefit analysis of whether it is worth revealing themselves and making any kind of outreach toward establishing formal relations. They could be part of a political structure that has rules about engaging alien civilizations and be forced to follow certain protocols. Or it is possible that the various ship designs UFO observers have consistently reported seeing represent different classes of vehicles from different cultures and a commercial private vessel may crash or reveal itself against protocols. Or it could be a Wild West situation where only the means and the will limit an alien civilization’s designs upon what it might like to exploit from the Earth.