"But we've always done it this way."
The Buddhist Though for the Day addresses this and similar manifestations of clinging.
While the Tathagata, in his teaching, constantly makes use of conceptions and ideas about them, disciples should keep in mind the unreality of all such conceptions and ideas. They should recall that the Tathagata, in making use of them in explaining the Dharma always uses them in the semblance of a raft that is of use only to cross a river. As the raft is of no further use after the river is crossed, it should be discarded. So these arbitrary conceptions of things and about things should be wholly given up as one attains enlightenment. -Buddha
All things are impermanent. What we have "always done" has not always been done nor will it always be done. It is simply the raft we have used for awhile to get from there to here. An interim measure that has served its purpose.
This clinging to the way we've always done things is the essence of conservatism. A blind need for permanence that fails to recognize that things are always changing all around us and in us at all times and in all places. Things that have served us well in the past become obstacles to moving forward.
"As the raft is of no further use after the river is crossed, it should be discarded."
As the European enlightenment-renaissance-scientific-industrial revolution went on the old ways of feudalism and mercantilism were abandoned to be replaced by nation-states, nationalism and capitalism. As Europeans crossed the ocean to settle the Americas they eventually discovered that the old ties that bound them to their former Kings and Lords no longer served a positive and useful purpose. Consequently, we broke those ties and moved on.
What drives us as individuals and communities to this clinging? We do it in our personal lives as well. We take photographs in order to hold on to precious moments in our lives. We attach to family, friends and relationships and all the while as we attempt to perfect them to our preconceived notions of how they should perfectly be we also resist the idea of change and potential... eventual... inevitable... loss occuring in them. We cling to our notions and idealized perceptions of the reality we create for ourselves.
Certainly fear and ignorance drive this. We fear loss. We fear not getting what we want. We tend to be ignorant of the inevitable impermanence of all things. Yet we see change happening and we cling in an attempt to resist that which cannot be resisted. We suffer as a result. Individually and collectively.