When I do the annual reading for a sign, I don’t have any information about you specifically. I don’t know that you have certain natal aspects or natal transits. But I know the astrology of the charts that I am looking at; which are developed intentionally for the reading I’m about to offer. I am able to prepare the report as a whole, based on a coherent reading of the sky. What I lose in certain elements of detail (your exact ascendant, for example) I more than make up for by being able to write as a whole person experiencing whole charts. This evokes the holistic or holographic property of astrology: I tell a complete story and pass it onto you, a complete person. They are likely to have a coherent relationship.
As an astrologer looking at actual charts and making decisions about what I observe, I can see the nuances of the relationships between different aspects and placements, and work with them in a way that responds to the subtlety.
To give an example, a computer program can dial in a pre-written interpretation for Pluto in Capricorn. It can dial in a pre-written interpretation for Mars in Leo, but few of these would account for the fact that Mars might be retrograde in Leo. When Mars is making an aspect, whether it’s retrograde or direct makes a BIG difference. And no programmed reading can put the whole scene together as one thought.
For example, what I can see as an astrologer looking at a chart is that there is activity in Capricorn; and that Mars has a subtle relationship to Capricorn (exaltation); Pluto and Mars are related (via Scorpio); and I can creatively interpret the whole thing together: how Pluto in Cap relates to Mars retrograde in Leo, for a given sign of the zodiac. Then I can go around the wheel and do it 11 more times, one for each sign. As a human, I can think back in history; I can remember stories clients told me about their experiences; I can include illustrations specific to a given unique condition in the sky; I can listen to my imagination and my intuition; and I can offer this collective wisdom back to you.