Stars? What stars!
Stars? What stars! Who uses stars? In the centuries preceding the adoption of the Tropical Zodiac around 214 AD by the Greeks, measurements of stars and planets (by position and rising factors) had already largely ceased. Tables of positions and lunations and eclipses had come into common use among the few who practiced astrology. Most astrologers had stopped watching the sky and making their own measurements.
Yes, from time to time, someone would recheck and make corrections, but for the most part astrologers of the western world were using tables for planet movement, for times of sunset, for the rising of planets, etc.
Today, I have had students who could not point out the visible planets in the sky, who could not relate the sky to the chart. That's how little many people pay attention to the natural world around them. So, 30 degree segments of the celestial equator is easy to adopt when you are using tables -- or computers.
Tables of longitude position also do away with the messy problem of declination -- the visual displacement of a planet away from the zodiac center line. Declination is the reason why, when you have a planet of the Ascendant, that a visual look at the sky will often show the planet already several degrees high in the eastern sky -- or perhaps it won't rise for another half hour or so. Three dimensional placement is not popular among astrologers who are not capable of truly understanding the spherical geometry factors of measuring the sky.
All of this confuses some early-studies astrologers. I understand this well and I solve the problem by not using signs at all. Once you do understand the mechanics of the sky, you'll know that the Sun's seasonal declination defines the signs "for the Sun." The Moon has its own nodal axis, yet few use the Moon's Draconic Zodiac. Nor does anyone use each planet's own personal zodiac as defined by its orbital nodal axis.
A lot to think about -- or to ignore. Perhaps its best to just use 30 degree signs as defined by the computer or ephemeris. Dave