Is Rashi teasing us?

Question

In Bereishit 3:22 Rashi says the following:

and now, lest he stretch forth his hand, etc.: And if he were to live forever, he would be likely to mislead people to follow him and to say that he too is a deity (Gen. Rabbah 9:5). There are also Aggadic midrashim, but they cannot be reconciled with the simple meaning.

In Bereishit 4:8 we see something similar:

And Cain spoke: He entered with him into words of quarrel and contention, to find a pretext to kill him. There are Aggadic interpretations on this matter, but this is the plain meaning of the verse.

In both cases Rashi is hinting to us that there is more to explore but is not actually giving us all the details. What exactly is Rashi trying to say with these two verses?

Answer 1

Rashi's job is not to provide Midrashim, even though he occasionally frequently brings them into his commentary.

His primary role is to provide a basic understanding of the Pasuk.

As such, if the Midrash is commonly cited (in Rashi's day, perhaps) and he feels it contradicts the basic understanding of the Pasuk, it makes sense for him to refer to it and reject it (which he does in other instances*). Similarly, if it's a commonly cited Midrash that distracts from the basic understanding, rather than enhances it, it makes sense for him to refer to it and refocus the reader's attention to the basic Peshat.

Answer 2

One explanation is that Rashi is not satisfied that his explanation fully addresses the question(s) on the verse, and references the Medrash to say that the Medrash's explanation does resolve the problem, but is too far from Peshat to be included. See here #9, and the sources quoted there.