The reason why we recite the paragraph of ציצית in the evening Shema, is because it makes a reference to יציאת מצרים, the exodus from Egypt in both morning and night.
The Gemara asks why we didn’t put the prohibition against taking interest or the commandment to take proper weights and measures in the Shema. These Mitzvot also mention יציאת מצרים.
The answer given by the Gemara is that the paragraph regarding ציצית has other important important ideas aside from יציאת מצרים. They are: Accepting the yoke of the Mitzvot, וזכרתם את כל מצוותי, the Mitzva of ציצית, as well as the need to beware of heretical opinions, sinful thoughts, and idolatrous thoughts. These are learned from the words,לא תתורו אחרי לבבכם ואחרי עיניכם, do not turn after your eyes or after your heart.
For this reason, the paragraph of ציצית was chosen to be part of the Shema.