To encourage spending, we need to introduce more ways to earn and also inform already earners to spend part of what they earn. They should have no problem spending bitcoins since they will be earning more. And if spenders are prudent or smart enough, they would be spending their bitcoins on things they can sell for more bitcoins, or things that help them produce more things they can sell for bitcoins.
And ofcourse, we know there are people who really want to spend their bitcoins but no reliable marketplace and fast payment system exist that they can do so easily This is what we should be seriously working on otherwise we shouldn't blame them too much for not soending
If Bitcoin is what you get paid at your work, or maybe you work to get paid in Bitcoin, there is no need to always swap back to fiat before purchasing some goods if they accept Bitcoin as payment. You will just send Bitcoin and get your goods; that will encourage others to use Bitcoin as well.
But if you have another source of income other than Bitcoin, you can decide to keep your Bitcoin to store its value for the future instead of just spending since you have fiat to spend on your basic needs; no need to use the Bitcoin. The consistent saving will be in the form of DCA to accumulate your Bitcoin.