Because a toiletry kit is a set of [consumable, replaceable] parts, used pretty much all at once (same 20-minute process every day), where each component is not often chosen over an equivalent. I'll go thru a half-dozen shirts throughout the week (and society will object if I stick to just one), but nobody will care if I use the same toothpaste/toothbrush/floss/razor/foam/shampoo/soap/washcloth every day for years (replaced only when used up, and then replaced with the same product).

We have a variety of clothes as separate objects, as they are interchangeable (society objects if I _don't_ swap 'em on a daily basis), and can get by without some because there are others present as replacements.

In support of your point, it's a matter of where the line is drawn as a practical application to the scenario. While the kit may be considered a unit wherein parts really are part of the same non-interchangeable application (well, at least for us Y-chromosome types) and for purposes of this example isn't broken down further, the reverse may be applied. Rather than a given shirt considered a single object, by defined convention it could be considered a part of a complete outfit. Having so few pieces to interchange - say, the dress shirt not an acceptable match to the swim shorts - he could reduce the total count by considering sandals/jeans/polo a single unit as none of that stuff much goes with anything else he has.

To wit: that's just where he drew the line between things forming a unit and things counted separate but used together.