Bitcoins are great to invest and trade. Why would anyone spend their bitcoins on Uber?
Because it's supposed to be money, dude, not a nut you squirrel away.
The solution is to immediately buy the amount of BTC you spent, secure in the knowledge that the BTC ecosystem is strengthened every time you do it.
Only problem is that creates additional theoretical tax overhead (supposed to report the acquisition even if you only owe on sell to fiat).. at least best it was explained me, I keep getting different answers from different CPAs.