They either try to claim their abilities can not be tested in a scientific environment or that the test is made to be impassable. Basically, "it's not my fault, it's their fault!" Which again, brings up how these certain celebrity status psychics are able to do it enough to make an income, showing that they do believe they can use it in a controlled way (at least when being paid, anyway).
To be fair, if a $1 million prize went to whoever could prove ghosts or aliens exist, it would still go unclaimed as well yet anyone could have some kind of unexplainable paranormal experience but there is no way to prove it even with cameras, audio and a scientist ruling out any other explanation. Same with aliens despite people claiming to have physical evidence or worked at Area 51 or something. To the normal science world, none of that exists.
Because, despite what some claim, it doesn't seem to be something that can be done at will. Occasional occurrences are real however. Also, since it seems to be a natural ability for many people, by definition it is not supernatural at all.
In the back of my head I know if any of the claims of aliens or afterlife existence were ever proven to the masses (some 7 billion people) to be undeniably true- our world would be very much ****ing rocked. Type of **** were most might think twice about going to their day jobs ever again.
It's not to prove the paranormal/aliens exist, it's: to any person who demonstrates any psychic, supernatural, or paranormal ability under satisfactory observation Basically take them away from their hidden earphones, leaked info, audience moles, and other ways they fake these things, and ask them to show under controlled conditions that they still have the ability And in 50 years, no-one has - because there is no such ability