Since the Ascendant or Rising Sign is the fastest moving or changing factor in the chart(roughly every two hours) it is also the most sensitive, picking up impressions from all over. It is your "feeler" or antenna, much like the Moon(second fastest factor), only more so, and at a more concious level.

As your first contact with the world(the Asc is your Earth or Gaia sign), it greatly influences everything about you, from the way you look and feel, to your thinking and relationships. Not taking the Ascendant into consideration when doing a chart is utter folly. Even the powerful Sun takes a back seat to it and all those blogs using the Sun exclusively in their work are doing everyone a great disservice.

Sun signs only became popular as of 1930 with R.H.Nayor, a British astrologer, and exploded with Linda Goodman's "Sun Signs" in 1968. It was easier to calculate Sun signs than Ascendants so it caught on rather quickly. Before that, it was always the Ascendant that took priority in a chart

Most people look and act more like their Ascendant than their Sun sign or any other part of the chart, which is reason enough to reinstate it as the most salient feature in astrology. This would restore credibility to this science/art by convincing disbelievers that certain signs rising produce noticeable similarities in appearance and mannerism. After the Ascendant, the Moon sign is usually the 2nd most obvious feature in a birth chart.

Astrologers or bloggers who leave out the Ascendant when assesing relationships(synastry) are leaving out the most important factor of all, so that their interpretations are rather baseless. Yes, Venus to Sun or Mars is important for affection or sexual compatibility, but Venus, Mars, or Sun to Ascendant is even more important. Everything goes through the Ascendant first before it hits the other planets.

The Sun being the strongest emitter is usually the first thing the Ascendant feelers will pick up, hence the importance of Sun/Ascendant comparisons. If your Ascendant is in a fire sign, for example, you will feel a natural attraction or rapport with those whose Suns are in fire. Air Sun signs will also be pleasing. You will also like Mars or Jupiter in fire/air but the radiant power will be a little less so than that of the Sun. Even planets like Venus or the Moon in signs compatible to your Ascendant will be pleasing or attractive for you.

Your Ascendant will always gravitate towards people or things that feel pleasing to you, at least initially. Whether this feeling lasts will depend on the other planetary comparisons in your chart. For more details on this go to the synastry section of my site, especially the article "Astrology and Relationships".