The average exchange fee to buy BTC nowadays is what, 0.2% or something?
So for a measly +0.2% on your expenses (e.g. a 10 pizza would now cost 10.02), you can buy everything with BTC instead of fiat, without losing any bitcoins. If everybody does this, how much do you think it will help Bitcoin to actually skyrocket? How does that compare to the 0.2% extra costs?
Depends where you're at. Not all countries have exchanges. You might wait several days to get money on one and pay $30-50 to transfer it if you're abroad. Sometimes it's not possible at all from the more obscure countries.