Agreed on the lack of evidence. There are thousands of retired officers and senior enlisted personnel. Why do only a few claim this?
FWIW, I have over 23,000 hours of flying time, about 5,000 of that military. I've seen a lot of strange things but all were explainable as manmade except one and that one was probably manmade too.
That incident was taking off from Miami and climbing up to 10,000 feet on the way to Nassau, Bahamas. It was a pitch-black night, high overcast and no Moon. As we were climbing, a narrow white beam like a laser shined directly into the cockpit from our 12 o'clock above us and played around the inside of the cockpit and our faces and upper torsos. I see the beam in front of us but not it's source. I contacted Center and told them we'd just been lased from 12 o'clock and higher than us. "Are you painting anything in front of us?" I asked. The controller said no, but didn't seem interested which indicated to me he knew but couldn't say for security reasons. Still, I'd never seen a white laser and couldn't explain not seeing it's source.
No doubt there are many cases of unexplained aerial phenomena.
I have never seen anything where I thought the best explanation was an intergalactic spaceship piloted by aliens.
If we have recovered alien spacecraft and alien bodies so have the British, Canadians, Australians, Russians, and Chinese.
It beggars belief that for all these decades there was a highly successful global conspiracy of silence.