This parable clarifies verse 36, as the introductory "for"(Gr. gar) indicates. The previous parable stressed the signs leading up to Jesus' return, but this one stresses the responses to those signs and their consequences. Life will be progressing as usual when the King returns to judge. Similarly life was progressing as usual in Noah's day just before God broke in on humankind with judgment (cf. 1 Pet. 3:20-21). Despite upheavals people will continue their normal pursuits.
"The special point of the analogy is not that the generation that was swept away by the Flood was exceptionally wicked; none of the occupations mentioned are sinful; but that it was so absorbed in its worldly pursuits that it paid no attention to solemn warnings."923
Jesus' disciples need to maintain constant vigilance since the daily grind, including distress and persecution, will tend to lull them into dangerous complacency. It is normal for even remarkable signs of an impending change to have no effect on people.
