Every asset that can be used as both a medium of exchange and that can be held for the sake of the returns it posses always serves multiple purposes one which is for savings for the sake of returns and the other for spending when the need arises. Primarily, bitcoin was invented to solve the problem that is associated with spending so if an holder of bitcoin decides to just hold and not spend his bitcoin, it is indirectly doing a disservice to all that bitcoin stands for.

Because people are more interesting in holding what promises them returns, it is safe to say that bitcoin is gradually becoming an asset that is better held for the long run than spent because holding it is more profitable than spending it. the fiat is there which is constantly loosing it value due to poor government decision and the issue of inflation that is ravaging the land and so, it is only reasonable to spend the fiat and keep possession of bitcoin which is far more valuable that the fiat.