Tree trimming is the act of cutting away parts of a tree primarily to improve it's appearance. Tree trimming is colloquially used interchangeably with tree pruning, but they are not quite the same. Tree trimming is aimed at improving the aesthetic appearance of a tree primarily and can be understood in the wider context of landscape management. Insofar as trees that are paid attention for their appearance are maintained more thoughtfully, tree trimming positively affect trees' health as well. That said there are good reasons to have a professional tree service trim your trees rather than a landscaper or gardener.
The first reason trees should be trimmed by a company specializing in tree care was already hinted at above, that is, tree care companies do not simply trim trees, rather, i trimming they brig their full wealth of knowledge about maintaining ad caring for trees to bear in the work. In practical terms this means that a professional tree care company will notice thigs about the tree that a landscaping company would overlook. This is because a tree care company is familiar with the particularities ad peculiarities of trees, they know what's normal, what's concerning ad what's abnormal but unconcerning.
Having trees trimmed professionally also ensures the trees will be trimmed with proper technique. Simply cutting away extra branches doesn't cut it. There is much more that goes into to proper tree trimming that just that. Professionals understand the science, that is the proper use of a tool, but also the art of or using it, which takes years of training and experience. Related to this, the tools professionals use are specifically designed to be used for tree trimming. Some property owners have similar tools laying around but many do not. And even those that do, simply cannot keep their shears, pole saws, pruning saws, loppers and so on in tip top condition. Pros do and have to, after all it's their job.
If you have trees whose growth you care about on your property, say fruit trees or ornamental trees you do not want to take the chance of having them pruned the wrong way. In the best case, they will not looks as good as the could with proper trimming, but the worst case is the tree sustains fatal damage. Replanting or transplanting a tree is costly and not always possible, and that ignores the fact that every tree is a singular living thing that can never be brought back.
A professional tree service will save you time in trimming your trees for you. You do not have to waste a weekend or evening doing unprofessional work. A pro will get the work done efficiently. They will clean up after they are done. They will also give you suggestions on things to look out for and be aware of to maximize the health and beauty of your tree. No matter how much effort and care you put into the trimming work, it will just not look as good as the work done by a professional.