He sees you as an equal, not his boss, and doing favors for each other won't change that. Would Wrex like to be your squadmate again? Sure - but he has his own problems and responsibilities. Shepard is his friend, not his eternal master and superior that he abandons his life to be a lapdog for (see: Garrus, who is a really nice guy I kept in my squad in all three games but has literally zero self-esteem and ruined his life out of his misguided idol worship of Shepard).

He has his own motives, his own desires, his own flaws, his own eccentricities, and they all exist for his benefit, not the player's/Shepard's.

Wrex is perfect and the best character in the trilogy because he's an actual character. It's a shame that 3 completely shits on that, has the geth completely reject those ideas to adapt to how the rest of the galaxy lives (which, by pure coincidence, corresponds exactly with humanity's 19-20th century Western philosophy regarding individuality and civics), and have EDI proclaim that they made the 'correct' choice by rejecting their old culture and concepts of self. Legion is a glimpse at a truly alien society, one that can't be called 'like humans, but _.' His interactions in 2 are truly wondrous looks into different ways of thinking and existence.

What does tali look like under the mask