It's more analagous to buying some gold for your investment portfolio than buying a fiat currency that has its inflation under control by a central government.
BTC isn't very good as a currency but acts as a deflationary asset over time (i.e. there is a fixed amount that can exist).
I, personally, hold BTC as part of my portfolio simply because of it's ensured existence and massive upside potential.
I wouldn't put a terrible amount of my net worth into it, but a small fraction may serve you well in the future.
Short story. Had the chance to invest 300k in 2012 (~$10 per coin). Didn't pull the trigger. Too much net worth. However, I should have used ~10k (maybe a little more). Wouldn't be nearly as worried about $ as I am today if I was just a little more conservative on investing up front.
The cool thing about bitcoin is that this is a shared decision made by everyone.
Ok, technically, it is made by the groups contributing the majority of compute power to the network. And technically, central governments can be representative of everyone and therefor enable that same shared decision making but that's kind of a bigger discussion.
The point is, changing the network to "add more" BTC is probably much more likely than breakthrough replicator technology that can turn hydrogen atoms into gold atoms.