The reason to use native plants in a garden is because they have co-evolved with local fauna and so are better for wildlife. To illustrate this, the Common Oak is host to 274 species of inverterbrate. That is a huge number. Here is a screenshot of the list (rotated to fit it on the page):
This is the reason we should be using native plants in our gardens wherever possible, because we need to start thinking about species other than ourselves. In a time of Climate Emergency and Mass Extinction, by providing habitat and food for our native wildlife, we increase its resilience. It also extends our thoughts beyond the confines of our gardens and into the wider landscape.