Dominicans writers like Simon Tugwell have observed that as charismatic a figure as Dominic was, Dominic the man does not loom nearly so large in the minds of his followers as the mission that he gave them. Unlike St. Francis, Dominic himself did not become the focus. The focus was and still is the mission.
Let me propose two (non-exhaustive) reasons, one external and accidental, the other internal and essential.
The external and accidental reason is St. Francis. The Dominicans and their founder are inextricably bound, by historical and ecclesiological ties, to the Franciscans and their founder. St. Dominic is indeed "one of the coy saints," in Fr. Tugwell's phrase, but his self-diminishment isn't particularly remarkable in the history of the Church. It's only when set next to the outsized impression St. Francis makes (largely due to his own acts of self-diminishment, it should be said) that St. Dominic's historical figure seems suddenly too small.
But it's not all just a trick of perspective. I think there is something in the very concept of the Dominican Order that works against having the founder loom too large. To quote the Master of the Order, Carlos Azpirpz Costa, OP, once more, that something is "the freedom Saint Dominic and his first Friars bequeathed to us."
The Fundamental Constitution quotes the Prologue of the Primitive Constitutions stating that the Order "is known from the beginning to have been instituted especially for preaching and the salvation of souls." Even before the idea of an Order came to him, St. Dominic was trying new and creative ways to preach the Gospel of Jesus Christ effectively. He saw to it that the constitutions of his Order permitted, even encouraged, his Friars to respond in similarly new and creative ways when faced with new situations.
From a Dominican perspective, then, there would be little to be gained by the first Friars through imitating their founder's preaching, either in content or style. The proper content depends on the circumstances, and the proper style depends on the individual preacher.
His prayer life was observed and preserved, but more as a description than a prescription. Neither St. Dominic nor his successors as Master believed that such personal habits should be imposed on the whole Order.
Dominican liberty leads to Dominican variety. A well-known expression in the Order is, "When you've met one Dominican, you've met one Dominican."
Here's some speculation: Generally speaking, Dominican saints resemble their holy father Dominic in not looming too large in the minds of those who came after them. St. Albert outlived St. Thomas, who had no great students of his own. St. Catharine had plenty of followers, but they could only follow her teaching; her prayer life and her preaching led her on a path for her alone.
So if St. Dominic was, by temperament and circumstance, destined to have his ideas outshine his person, I think he has bequeathed that same destiny to his Order.