Yes i think that selling bitcoin is just like "burning money". You are just withdrawing or spending your bitcoin instead that you could have much more in a near future, i dont know why people still spend their bitcoins, i just prefer to hold them all until it reach a nice value.
By the way, i have a wallet with 0.10 so everytime i have an emergency or i just need to buy something inmediatly i use that wallet, but i dont like to spend it.
I agree with people saying that if you sold your bitcoins, you are losing the opportunity of its value to increase but this is on the assumption of the prices increasing everyday. By just looking at the charts, the price of bitcoins last week were around $3500 and right now it skyrocketed up to $4000. In just a matter of weeks, the opportunity of your bitcoins increasing were superbly affected and this results to a loss on your part if you withdrew it.
What you said is correct. The reason on why I earn bitcoins is for me to withdraw it when the need arises. For example, I ran out of fiat due to paying obligations and I need extra cash in order to pay something important, I will use my bitcoins and convert it for me to sustain myself and pay my existing debts. All of us here have their own reasons on why they earn bitcoins and I see no problem in converting it to fiat for something far important.