Here's why:

* Evolution is driven by natural selection: Evolutionary changes, like the development of new characteristics, happen primarily through natural selection. This means that individuals with traits that make them better suited to their environment (like finding food, surviving predators, or reproducing) are more likely to survive and pass those traits on to their offspring.

* Competition is a key factor: Competition for resources like food, habitat, and mates is a major driver of natural selection. When resources are limited, individuals with traits that give them an advantage in competing for those resources are more likely to survive and reproduce.

* Traits develop without conscious need: Organisms don't "develop new characteristics unless they have to compete". Variations in traits arise randomly through mutations in DNA. Whether those variations are beneficial or detrimental depends on the environment. If a trait helps an organism survive and reproduce better, it's more likely to be passed on to future generations.

In summary: Evolution is not about organisms consciously developing traits to meet a need. It's about random variations in traits being selected for or against based on their impact on survival and reproduction in a given environment. Competition for resources plays a significant role in this process.