Let's say all magic is a heap of hooplah, it'll still function, and should still be practiced for a few very important reasons
Magic involves cultivating mental focus and thinking about the steps needed for a required result.
After performing a well designed spell you sort of know what you need to do to accomplish your result
People are influenced by the placebo affect. They believe it must work and therefore it does
A woman who casts a spell to make other people see her as more beautiful walks confidently. She feels pretty enough to get some new flattering clothes, try a new haircut. She can behave differently with men. Does it matter that no one's optical nerves or visual cortexes were actually affected? No of course not, she wouldn't have had the confidence to go forward if she hadn't cast the spell though
A man who needs a job casts a spell to get one. He feels sure that he will get one now, and while performing the spell, he imagined the perfect interview and the way his resume would read. Surprise, surprise, he is confident and relaxed during his interview and he may send out more applications because he is sure something will come up. He also put a lot of focus in what needs to be done before hand. He gets rescued from unemployment no miracles needed.
A man trying to attract a lover casts a spell. He is now actively looking for a partner, is more likely to flirt. Is not sure of rejection and if he is rejected believes the relationship was not meant to be. He is more likely to find a date and less likely to feel stressed about doing so.
People can alter their realities of what happened in the past to fit their beliefs. If I cast a spell to protect my home in a hurricane. I will be pleased in many different circumstances. If nothing happens to my home I really feel like a big shot. If only superficial damage happens, then the spell must have done it's best. If the insurance company pays out quickly I will still consider it a success because it protected my ability to live at home. And if only my family is ok, well isn't family what makes a home and not a house which can be rebuilt?
If I put a lot of thought in what needed to be done to protect a home, I would help the spell along. Maybe I feel a tug to move all my belongings to the top floor, evacuate my family, and so on.
A spell will always work out in some way in our minds. Sometimes that means that it let's us focus on the positive and the truly important and move forward. Positive thinking can affect cognition and allow resilience and a protection against depression in times of trouble
So magic can actually change your life and promote healthy mindsets. Next question, why are some people just so scarily good at divination (assuming magic isn't real). I'm going to just focus on cards like tarot to save time
I'd like to argue that your future is actually pretty predictable. You are born into a geographic area with certain opportunities and to parents who help shape your future. You then change your life with personal choices but you probably can guess the consequences of your actions. This is of course barring the truly unexpected, such as lottery winnings and freak car accidents.
Card divination may work off of a phenomenon known as priming. This is an unconsious form of memory retrieval, where an image or a string of words can bring up memories of things associated with it. For example if I say dog, and ask you to tell me the first letter of a three letter word ending in -at, you'll probably say it's c, as in cat.
This means that the imagery brought up by a card or even a medium's words will bring up relevant information from your brain subconsiously. And that's amazingly important. If a card tells you that there is an untrustworthy fair haired man in your life, it matters a great deal if you think it's your boy-friend or your neighbor
Since people generally have a feeling of where their lives of going, even if they'd rather not, it's easy for the subconsious to pull up relevant information associated with a reading. It really is a snapshot of what you think the world you live in is like and where you feel you're going.
It's really fortune telling and psych evaluation combined.
I'm not making this post to demean magic. In fact I feel I'm doing the opposite. I'm showing that it must work and can change your life as well as give you valuable information.
I have seen stuff that couldn't happen because of personal choice after casting magic so I know it's definitely real, but I thought some people might be interested in this take.