(First wears tin-foil hat). It may be more likely that we are under observation and a mature inter-stellar space faring alien civilisation has commandments not

(First wears tin-foil hat). It may be more likely that we are under observation and a mature inter-stellar space faring alien civilisation has commandments not to interact or interfere with the primitive natives. They occasionally mess up and then the UFO's are seen. But their propaganda department clears the mess up.