When did shower gel replace soap (in Ireland)?

Producers like shower gel because profit margins are higher, plus you use a lot more of it - most of the product is washed down the drain, literally. What's not to like, from a producer's point of view? They sell it by trying to promote the idea that it is more hygienic, though they have to be careful about how they suggest this, since there is in fact little objective foundation for the claim.

One advantage that shower gel does offer is convenience - it makes a perfectly acceptable shampoo, so the one product can deal with both your showering needs. Obviously, though, producers would rather sell you two products, so they tend not to stress this fact, except when marketing to particular segments - specifically, men in the 30s and above, for whom convenience is a big selling point. Producers will market a "2-in-1" product to this segment although, truth be told, pretty well any shower gel will function well as a 2-in-1 product.

Shower gels are mostly water-based (the word "gel" is a bit of a misnomer, strictly speaking) so they are better vehicles for delivering moisturiser than hard soap is. for this reason if you have very sensitive skin shower gels may offer advantages. But I stress "may"; the marketing of shower gels as luxury items often involves the additions of (natural or synthetic) fragrances, essential oils, etc, which have no cosmetic or hygienic function but make the user feel pampered. Particularly in the cheaper shower gels, these can be a bit hard on the skin, and this may offset any moisturising benefits.