1 Cor 7 raises a number of interesting interpretive issues, most of which I'll ignore in this post.
1) One issue is why some Christian couples were either deferring marriage, or abstaining from conjugal relations. Here are two of the more plausible explanations:
i) Perhaps some of them operated with an overrealized eschatology. They thought the new covenant ushered in a new world order, rendering sex and marriage obsolete. Kind of like the Shaker cult.
If so, I assume it was some of the Corinthian women who took this position, inasmuch as it's hard to imagine men dreaming that up.
ii) There may have been anxieties about the future, caused by concerns about famine or other socioeconomic insecurities. Because sex normally produces children, would it be prudent at that time to refrain from having a child or expand a preexisting family in case socioeconomic conditions might make it difficult to support your dependents?
I'd also note that these are not mutually exclusive explanations. Maybe both were in play.
2) Another issue is whether the statement in v1 (“It is good for a man not to have sexual relations with a woman”) represents Paul's position or the Corinthian position. Is he expressing his own viewpoint, or is he quoting from their letter, as a foil? There are good arguments, albeit inconclusive, for supposing that Paul is quoting or summarizing the Corinthian position at this juncture (see Thiselton).
On the face of it, it would be odd for Paul to stake out the position that it's good for a man to avoid sexual relations when he immediately proceeds to insist on conjugal relations. It's possible, though, that Paul has something more specific in mind. So the tension may be superficial and illusory.
3) It's striking that in his justification of conjugal relations, Paul doesn't appeal to procreation. There may be a couple of reasons for that intentional omission.
i) Paul makes the point that sexual enjoyment within marriage is good in itself, and not just a means to an end. It doesn't require procreation to justify it. It isn't even secondary to procreation.
ii) Paul is addressing Christian gentiles. Converts from paganism. In Greco-Roman culture (in contradistinction to Jewish culture), sex was bifurcated. Basically, men had procreational sex within marriage, and recreational sex outside of marriage. The purpose of marital sex was to produce legitimate heirs. But for sexual enjoyment, men had recourse to courtesans, mistresses, prostitutes, and slave-girls. Your range of options depended on your social class.
a) One likely reason Paul doesn't discuss the procreative rationale for marriage is because his Corinthians correspondents already accepted that rationale. The problem, though, is that they restricted marriage to procreative intent–in contrast to premarital or extramarital recreational sex.
b) Apropos (a), Paul is opposing that bifurcation. Sex for pleasure is good, but that, too, is confined to marital sex. Marriage is the proper setting for procreational and recreational sex alike.
There may have been gentile converts to Christianity who thought it was just fine to continue their former practice: procreational sex with your wife, but recreational sex with other women. If so, Paul is correcting them.
Incidentally, this may also be what Paul had in mind concerning his enigmatic statement that an elder should be a one-woman man (1 Tim 3:2).
iii) Of course, this only works if both spouses understand and honor their mutual roles in that respect, which is why Paul goes on to stress conjugal relations as a reciprocal duty.
Ironically, some "evangelical feminists" have turned this upside down. Paul says the husband has a duty to his wife. They say the wife has no duty to her husband.