Both Dattaatreya and Suka are sons of well known sages in Hindu puranas. The concept of son itself has a hidden meaning, as in other familial ties. A son ofcourse carries forward the school of thought that the father propagates, which is exactly what these two great sons did.
Dattaatreya is the son of Atri Mahamuni. The name of the sage Atri itself -- A-tri: without three or beyong three -- conveys the spirit of one who has transcended the three levels of consciousness (not just beyond the three characteristics of Sattva, Rajas and Tamas). Datta-Atreya means, someone who has been adopted by such a sage and AnaSuya, one who is beyond Asuya. It is said that Brahman himself had been Datta (taken as a son) by such a couple. Datta-Atreya is said to be the sage who formulated the basic concept of Advaita: namely, Aham Brahmasmi (Thou art Brahman).
Suka is the son of Vyasa. Vyasa is the divine sage who compiled the vedas and wrote the Mahabharata containing BhagavadGita and VishnuSahasranamam. Vyasa literally means the divisor of vedas. Suka is known to be his son, who had transcended all the stages of consciousness from birth itself. Suka narrated the Bhagavata Purana. The narration has well known chapters like Gajendra Moksham, Prahlada Charitam, where he not only conceptualized the method of Jnana (like the original prayer to nirguna Brahman by Gajendra) and of course, the method of Bhakti (where else but the pinnacle: chapter 10?) in the story of Lord Krishna.
An Anecdote about Suka: It is said that Suka if he heard even the name of Radha, would go into samadhi. So, in the whole Bhagavatam, there is no mention of Radha-Devi. The questions put forward by Parikshit were such that no mention of Radha could be made by Suka when he was answering the story.
It seems that the Atri-Dattaatreya are more abstract to understand by ordinary human beings. (This is even though the teachings are very simple, like the 24 natural gurus of Lord DattaAtreta.) So Vyasa-Suka had made the ideas into a form that is more concrete, and possibly easier/simpler in another way. The result was a concept of Bhakti which could be understood by the multitudes.
It should however, be not be forgotten that the Avadhuta in the Avadhuta-Yadu samvadam, which occurs at the end of Bhagavatam, is none other than DattaAtreya. So by inserting that dialogue in a later chapter of Bhavatam, Vyasa-Suka made the wonderful reader-friendly assumption that a reader who has read/listened to Bhagavatam till that chapter is sufficiently mature to understand the Advaitic concepts of DattaAtreya.