Discrepancies between smell and taste
The food that you eat regularly is something that you are used to. You know exactly which smell combines with which taste ... but that does not imply that the chemicals you smell are the same that you taste.

If you had been eating your whole life long fragrant soap with apple smell, you would wonder about the taste of real apples as you wonder right now about the taste of apple soaps.

There are a lot of different substances that are responsible for the special taste of everything you eat. You can find more about flavor or aroma compounds on wikipedia.

In contrast to real fruits, fragrant soaps and other industrial products with a certain smell only contain those substances that are responsible for the characteristic smell of e.g. fruits (often only the main one or two aroma substances or even only synthetic aroma substances that smell similar to the natural products).

But as not all products that shall smell like certain thing also need to taste like those things you only smell the "apple" but you won't taste it.