Perhaps it is the semantics of referring to low 20s. In those times the general age of marriage, even for guys, was between 19 and 22. (Usually, though, at least 20 and not too infrequently 23.) The low 20s in your circles today I would guess is generally most often beginning at 23 or so, no?
What do you mean by intentional? It may have been somewhat intentional in the sense that people wanted to accomplish certain milestones prior to marriage but perhaps more so it kind of slipped without people explicitly deciding to get married a bit later.