What are some of the concerns you have over Bitcoin besides the fact that it is "new" and "strange"?
I remember when people thought debit cards were "new" and "weird". Do you realize that most of the "dollars" you think you own are no more than 1's and 0's in a database? Your ledger balance with your financial institution is your store of capital. Your debit card or any Federal Reserve Notes you withdrawal is your transaction currency.
When you think you are taking your "dollars" and giving them to McDonalds by swiping your debit card, you are actually authorizing your financial institution to decrease some 1's and 0's in your ledger and increase some 1's and 0's in McDonald's while transacting through a mutually trusted network owned by VISA who charges a fee. If you think that system of exchange is efficient and beneficial to you then you can keep using it. If someone else would rather retain control of the entire transaction between the two interested parties and pay a minimal amount in fees they can choose Bitcoin.
Again, I would restate that normal people don't "invest" in currency. The people who do so are speculators or commodity traders. There is some amount of risk inherent in any occupation and I won't criticize them for their chosen profession as long as they face the consequences.
Do you think the folks in Ukraine who's currency has cratered and who are subject to currency controls value some of the aspects of Bitcoin right now?
Unless you exchange your dollars for something else, you are "investing" in the dollar. There is no way to avoid "investing" so long as you own anything.
As to why, consider how currency develops. Once, it was a symbol for concrete value. One dollar once meant one dollar's worth of gold securely held. As the need for currency outstripped the pace of gold aggregation, currency became backed by the faith and credit of the issuing government. Hamilton instinctively knew this hence his plan of rapid payment of the revolution debt coupled with a stable and controlled central treasury. This convinced the world that a dollar was not an arbitrary piece of paper but a monetary note of value.
Bitcoins, on the other hand, are not backed by anything. When tulips were introduced in Holland, they were a novelty item that quickly became desired in an stunning crowd movement. The value of one bulb became extremely high and people started trading in tulips. The problem was - it was a tulip bulb. Anyone could set up shop as a tulip grower and dealer, much like Bitcoins. They are simply created by software (referred to as mining), have no backing, no protections, many mining trojans exist. Anybody can create them. Bitcoins simply had value because somebody convinced another that they did.
A dollar on a debit card can be exchanged at any time for a predictable amount in “real” dollars or goods and services. A dollar on a debit card has the backing of the US Treasury. It has the protections of a dollar, the regulations of a dollar. This is key for a currency - a predictable value and historical worth.
Bitcoins have gone from $2 to $1000 in a single year and now plummeted to $300. That is not a currency. No predictability, no historical consistency of value, no way to transfer and exchange for goods at a known, predictable rate. There is no division of labor. Anyone with the right algorithm can let a computer churn them out.
Bitcoins are very similar to a massive ponzi type scheme. A few people initially created something of limited availability with no intrinsic value, convinced others of its worth, traded like mad to drive prices up, and are now walking away with real dollars while many will be left with worthless software.