It is not quite so simple. Standard economists worry that if inflation becomes too low (or if there is deflation), incentive to hoard increases and incentive to invest drops, which could lead to negative growth, the bête noire of capitalism.
There is inflation because there is money. The purpose of money primarily is to facilitate trade. That is not to say trade cannot happen without money. Money just makes trading easier.
From that perspective, there is no reason for inflation at all. This is because money is just an intermediary for the exchange of goods.
Now, on the argument that deflation leads to negative growth, that is true to a certain extent but mostly because the basis of growth is consumption, to the extent of excessiveness, regardless of factors like environmental degradation which may lead to our eventual extinction because of climate change for example.
Capitalism when driven by greed will lead to our eventual demise because there is no limit to greed. The only way out is to realise this before it is too late.