In the study hall, who rises for whom is not a small matter. Standing signals reverence. The Rabbis watched very carefully whom they chose to honor in this way.
Rabbi Zeira was once seated at the Beit ha-Midrash, the house of study, when a man entered who had recently been appointed to a public position. The man was not a scholar. He had been appointed because he was wealthy — because he had paid for the office or his family had influence.
Everyone around Rabbi Zeira rose. He remained seated.
He was not rude to the man. He simply refused to honor wealth with the gesture reserved for Torah. Appointments by money deserved courtesy, not reverence.
Later, in Caesarea, Rabbi Isaac ben Elazar faced the same situation and did exactly what Zeira had done. He did not rise.
The other sages, instead of rebuking them, praised them. The tradition preserved the moment in Gaster's Exempla #276 precisely because it drew a line. The Jewish community was built on distinctions that refused to collapse. A wealthy appointee was still a wealthy appointee. A Torah scholar was still a Torah scholar. Rising was a blessing spent on one, not the other.
Study honors substance. The Rabbis would not cheapen the gesture by spreading it wide.