Are you serious? You know, not being a Cat 1 racer does not equal "complete inexperience." Perhaps you take your own considerable training and experience too much for granted.
Most people have a pretty good sense of the level of effort they're putting out as they pedal, but I'd submit that unless they've ridden with a computer or made a point of counting pedals strokes, (or are musicians) most riders wouldn't have the slightest clue what there cadence is, ever. People ride for years without paying any attention to cadence. Combine that with the fact that conditions can vary very gradually, especially on essentially/seemingly flat roads, it takes quite a while (relatively speaking) before many riders even realize they've slowed down or speeded up.