If the price weren't fluctuating at all, I would have all of my money as possible in bitcoins. In fact I tried during the long 5$ period last year. I don't use myself as an "investor", but as an user that has its own bank. There were several potential purchases last year that I didn't make because I had to go to the bank, do transfers, etc.
Potential clients includes investors, but also users that just want to save in bitcoins. It doesn't matter that merchants convert the money into USD, the other advantages still applies.
Also, PayPal is very expensive for very small purchases.
Again, you are missing my point. Because this fluctuates so wildly, anyone who wants to use Bitcoin IS an investor.
Imagine if the USD (or pick a currency) fluctuated wildly in reference to CPI (consumer price index)? One would be required to essentially become a forex trader in order to maximize everyday purchases. This is why Argentines & Venezuelans trade for USD (on a massive black market), because it's stable comparatively. Bitcoin does not enjoy this type of stability.
It is an investment tool that can be used to make purchases from merchants who use BitPay to hedge, nothing more.