Well, currency will always be worth less than the money it's backed by, simply because it's a claim on the money, not the money itself.
Moreover, currency is commonly issued via lending, which means interest will also be required. If I lend you the first $100 and charge you 5% per year, for 5 years, where will you get the extra $25 in interest to pay me back? You'll need to take out a new loan to pay back the old loan + interest, and so on.
Definitely agree on the fact that currency is inherently less worthy since it's only a claim on money, I'm however not sure whether it should *keep* losing value after being issued the first time, meaning that it losing value is one of the core qualities of currency instead of it being simply a result of how things are with the present fiat system.
To keep things tied to Bitcoin, would you categorize chaumian ecash as currency?
Well, in my opinion, as long as currency is nothing but a claim or a receipt for money, it's inherently prone to keep losing value.
I'm not educated enough to answer the second question, so I won't pretend I can answer it.
