Oh dear
Perhaps your parents thought that it was no bad thing for children (or you, especially) to find ways to surmount obstacles in their path, financial or otherwise.
They may possibly have had an upbringing themselves which taught them to make their own way regardless of family having the means to 'help out'.
I myself have refused on occasion, to lend money (and I have a not insubstantial amount of savings at my disposal) to one child in particular as they are wasteful and make no effort to budget on their salary. Needless to say, that AC was rude and bitter when I declined.
Were your parents saving it in case they needed long-term care away from home? Could you ask both or one of them for answers without them getting cross, after all, it's their business what they choose to do with it?
However you manage this delicate situation, I hope your relationship doesn't come under any strain.
Least said, soonest mended...as the saying goes but I do understand your feelings in the matter.
Fortunately, my parents had very little and left nothing, so we children had to make our own money and manage as best we could, which turned out well for all 3 of us.