The infrastructure that allows money to have and keep it's value has to be paid for somehow. Deflation makes it hard to get the economy going again. When your money will be worth more tomorrow than it is worth today, why would you spend.
One analogy I like to use are the roads. If everyone paid for road usage on a per mile basis, then you would have some people possibly paying next to nothing for the roads. However, they get all of the security of having roads available whenever they need them, even if they don't necessarily need them all the time.
Same with money. If you save, you are taking advantage of the fact that those engaged in economic activity and whose activity supports the value of your savings. If that economic activity ceases, why should you expect the value of your money to remain the same.
I don't think there is any reason why intertemporal transfers of wealth (fancy phrase for saying money earned at one point is spent at a different time) should be costless. it's one of those things that some people believe to be obviously right, but there is no a priori reason why that should always be the case. Most forms of wealth degrade over time (with the exception of land and metals like gold) so the idea that one's wealth just sustains is fairly unusual. Think about it, you car depreciates, houses fall into disrepair and ruin, farm animals die if they aren't taken care of. Most people take it as a given that their wealth loses value all the time. No reason why money should be any different.