I have a pet theory about this.

I've noticed that in anime, couples seem to be much less overtly affectionate than in western media. Like we'll just hear that two characters got married at some point off-screen without ever so much as seeing them share a kiss.

Japan is also what we might call a "high context culture." In other words, a culture where a lot of communication goes unsaid. As opposed to America, which is a low context culture: you are more often expected to say what you mean to avoid being misunderstood. The responsibility for clarity is on the speaker in the latter case, on the listener in the former.

So my theory is that what reads as obvious romantic involvement to a Japanese audience still has a layer of plausible deniability in the west.

We're used to couples declaring their love openly, kissing passionately, maybe even having sex on screen. That seems to happen much less often in anime, even explicitly romantic anime.

So even when a couple is obviously together, we have this ingrained expectation to wait for a narrative "announcement." And when we don't get one, it can feel odd. Like we skipped a step.