Caviar was eaten by those who truly enjoyed it and it was done so in the purest way...
Now it is a status symbol very costly and consumed by people who love it and those who don't...the melba toast, egg, and onions started when those who couldn't eat caviar in its pure form, added it to tone down the taste of the "fish eggs"
So I reiterate, if you need onions and eggs to enjoy your caviar, ask for a pack of peanuts instead and leave the stuff to the ones who truly know how to appreciate quality.