The Mirror of Erised reflected people's desires. Those desires came in all kinds, but who would associate them with going to the toilet?
Yet if someone could not use the toilet, they would know the agony after being constipated for a few days. Buddhism held that wanting something and being unable to obtain it was a form of suffering. Many pursued the Philosopher's Stone; even if they had so much money that they had no need for transfiguration into gold, they still craved the immortality it offered.
When women looked into mirrors and saw themselves growing older day by day, they were willing to try anything to slow the process. Yet preserving their beauty did not necessarily allow them to hold on to the love they wanted.
Set against desire was conscience. Some had that conscience but lacked the ability; others had the will, but because they had been poor in their youth, they lacked the means. Once they achieved a little success or the world around them changed, once the shackles binding them vanished, that "person" changed as well.
The Thought-Reception Charm worked on everyone. Both Voldemort and Harry wanted the Philosopher's Stone. If it simply accepted every desire, then Voldemort, who had arrived before Harry at the Mirror of Erised, should have obtained the Philosopher's Stone first.
So the Thought-Reception Charm must have had another restriction: only those who wanted to find it but did not intend to use it could obtain it. This was also one of Albus Dumbledore's tests, a test of whether Harry's heart was as Albus hoped it would be.
It was like Double Transfiguration, an advanced form of magic. Pomona had never considered before that magical creatures with lifespans longer than humans could take this path.
It was a lonely and lengthy road.