I believe that if the main driver of value was usage as currency, the market would've already shifted towards other systems, given the current problems with network congestion and high fees.

This brings us to the next issue: When there will be a hardfork (possibly soon), there technically won't be a "Bitcoin" anymore, but rather "Bitcoin Classic" and "Bitcoin Unlimited". The market will have to decide which one to make dominant. Either way, value will be moved out of Bitcoin and into fiat and other cryptos, simply as a precautionary measure. I certainly know I will be doing that.