Just the nature of the beast, as they say - genetic information in its DNA, like genetic info for blue eyes or purple leaves or ginger fur on a cat...

plane trees do this. they 'ping' off small bits of bark to expose fresh areas where they can swap oxygen and carbon dioxide to survive.
and it is a genetic thing as Bamboo says.

Is that why Eucalypts do it too, Seaburngirl?

I suspect so, dusty areas or areas prone to fires tend to have plants that do this.

There's a maple that does it too, can't remember its proper name, the paperbark one.

Acer griseum

Some tropical trees do this to remove heavy coats of epiphytes and parasites. I have no idea why hardy ones like birch and Chinese elm do, though.

Probably and adaptation against moss and lichen build up.

I forgot! Temperate zone trees have their own epiphytes.

A friend of ours has a huge eucalypt belonging to a neighbour at the bottom of his, fortunately, large garden garden. It sheds long strips of bark in good quantities. They make marvellous fire lighters in his new wood burning stove. He used to curse the bark raining down from on high, now he is quite pleased the tree is there. Even though there is much speculation on how many garden sheds it will take out should it fall! It has rather an alarming lean to it.!

And there's another reason for shedding bark! Eucalyptus are a very fire-dependent group of species. The shreds of bark hanging from the trunk and piled around the base encourage ground fires to quickly turn into hot crown fires. Eucs recover quickly from such fires, but other trees are much slower--so the Eucs win the "space race", in the forest.

Cor, fascinating stuff, I love this site...

Interesting!