In my story, this one species is able to manipulate magic. (twenty kinds of magic, more specifically) They're only able to manipulate one kind of magic that they inherit from their parents.
On the other hand, another species (humans) has no access to magic and cannot learn it, and focuses more on weapons for their fights. They can use objects that have magical properties (such as staffs, amulets, armor, guns, etc) but can't cast magic from their bare hands like the other species can.
As some background, the story takes place on Earth in the year 2150, where many large cyberpunk cities are scattered around the remaining habitable areas of the planet. Aliens have finally discovered the planet and have landed, hence the other species i mentioned earlier. Technology has advanced a lot, thanks to the magical species coming to the planet and using their magic essence to make futuristic weapons, appliances, machines, robots, etc. That may have been too much or too little information, i'm not sure how much you all need.
As for the question, i guess it's sort of hard to get factual when it comes to magic, but i'd like a scientific, plausible reason behind my question.