Arborists see trees very differently from how most of us see them. They know their trees very intimately, and by botanical name. Arborists know how big particular trees get, both tall and wide, and if they are likely to develop structural deficiency or aggressive roots. They can tell us which are deciduous, which are evergreen, and which are messy with foliage, bloom or fruit.
Some arborists are happy to divulge a bit of history of some trees, whether exotic or native. They might tell us where the exotic trees came from, and why they were imported. Some trees were brought for timber. Some were brought for fuel. Some were imported just because they were pretty. Some naturalized, and now impose on the natural ecosystem. Natives try to adapt.
Since they know the innate characteristics of trees, arborists know what their cultural preferences are. They know that some are understory trees that prefer the company of other bigger trees. Many others are those bigger trees, that want to dominate their respective landscapes. Some want plenty of water. Many of the natives do not want much more than annual rainfall.
An arborist might provide you with way more information than you ever thought you wanted about your seemingly innocuous trees.
Besides all that, arborists are a weird breed that really enjoy their work. Arborists like me simply enjoy diagnosing problems with trees, and prescribing corrective arboricultural procedures. Those who climb trees to execute such procedures are much more involved! Their work is as demanding as extreme sports, and they take it very seriously. They must. It is their profession.
This view of a big box elder, Acer negundo, from above, which I got from the edge of a bridge, might be that of just another day at the office for other arborists.