In the Liturgy of the Word at Mass, frequently the Psalm that is recited, after the Word has been read, is not read entirely, but only certain verses are chosen out of that psalm.
And again, on some Sundays when the reading of the Gospel is long, there is sometimes an option to skip reading parts of it as well. This also applies to the verses in the O T books where a verse may be read from one book, and the next verse read from another book. There is a good deal of skipping around in the O T.
We aren’t really required to read all of any passage of scripture privately or publically in the Mass. We may choose to read passages that fit our thoughts of the day. And apparently the verses discussed did not exactly fit in the thought of the liturgy for that day. But maybe sometime in the future, someone/group may decide that it does fit. So it really is basically a rational decision of the group who decides what verses fit for the day and what do not. But that doesn’t imply that the verses omitted are not important, but just not applicable for the spirit of this moment.
The verses omitted are instructional, while the other verses are inspirational. It may have been thought better for omitting them for the sake of those who are more sensitive or even scrupulous who would be bothered by these verses, and then might not go to Holy Communion.