All flowering plants use animal vectors for pollination and/or seeding. Flowers have sweet nectar that attracts insects which, in the course of collecting the nectar, pollinate the flower which grows into a a fruit or seed pod that animals or birds eat. The seeds are distributed by the those creatures as they pass through their gut and are “ejected”.
The trees did not “decide” to have these features, nor do the insects intend to pollinate the plant or the animals to spread the seeds. Rather, the entire intricate design is that of the Great Engineer of the Universe.