I suspect one of the reasons for variation in taste-bud receptiveness (apart from the variations in quality of the rocket) is the variation in salt intake amongst us. Many years ago I decided to not add salt (sodium chloride, specifically) to my diet and just rely on the fact that it features in most foods and is relatively higher in things like cheese and salami.

I found that tomatoes were suddenly as tasteless as Iceberg lettuce; I'd previously always given tomato slices the merest smidgeon of salt. But I persisted with the diminution of salt in my diet and the flavour of tomatoes gradually came back; more dramatically with home-grown ones rather than supermarket ones, of course.

Given that the western diet is riddled with high levels of sugar and salt (sodium specifically) it might be that those of us with higher exposure to salt are (relatively) limited in our perceptions of "natural" flavours.

Cheers, Rowan