If you earn bitcoins in this manner, unlike those who have to convert from fiat or have no other source of income, why don't you spend them aswell, since you'll keeping earning more?
That is because in sales, you always don't get the same amount from what you're selling. It could be good and better this time but by the next month, it could be like a ghost month in sales.
You know what I mean with that? it's not always good when someone is into a typical business and this is like that. So, keeping some bitcoins from those sales is a must as if you're also saving for the rainy days.
This attitude towards finance is the same for those people who usually gets broke who continue to spend money because they'll have a salary to come.
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.
Even with that, everyone is free not to follow such encouragement if they like to keep holding. The scarcity of bitcoin makes us all want to hold it.