This is true, but the definition of "really want" changes if everything you can buy is subject to deflation in your currency of choice. If you believe Bitcoin will keep rising you will defer every expense until the last possible second and many transactions you will defer and later find that you do not need to engage in them, thus there is less commerce ongoing.
How does a rational consumer justify going out for dinner on Friday if on Sunday they expect the date to be 15% cheaper, and Tuesday to be 20% cheaper, and so on? It is like the pain of finally biting the bullet and buying a new computer in the 90's knowing it will be cheaper in 3 weeks, but on every transaction you make.