They can be changed. None comes without a cost. One characteristic of money that we take for granted is price. Price is money's way of talking about comparative value. In the world of money, things are worth more if they are scarce or if they make money.
Volume drives prices down.
Things that are universal, that anybody can do are treated as worthless. That means that within the pricing system used by money, we can never really place a high value on decency, caring, loving, learning, neighboring, rearing children, caring for parents, or being involved as a citizen. Unless of course decency and caring and all those other things become really scarce. We have to step outside that pricing system in order to value the things we really value. Time Dollars do that.