Scientific reason for calling water Oxidane

IUPAC doesn't actually stipulate that water must be called 'oxidane'. See, e.g., p 85 of Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005 (Red Book)

The names ‘azane’ and ‘oxidane’ are only intended for use in naming derivatives of ammonia and water, respectively, by substitutive nomenclature, and they form the basis for naming polynuclear

entities (e.g. triazane, dioxidane). Examples of such use may be found in Section IR-6.4 and Table IX.

Note that the Red Book doesn't prescribe any kind of 'preferred' or 'official' name, so there is no rule saying that the 'official' name is oxidane. If anything, the quoted text strongly implies that water should be called water. And indeed there are a few examples of 'water' being used as a name in the Red Book (you can ctrl-F).

Since water is not an organic compound, the corresponding nomenclature rules for organic chemistry (the 2013 Blue Book) also do not select a preferred name. However, IUPAC tentatively use 'water' as the name for H2O:

The common names water, ammonia, [...] are used in these recommendations but their use as preferred IUPAC names is deferred pending publication of recommendations for the selection of preferred inorganic names; thus, no PIN [preferred IUPAC name] label will be assigned in names including them.

So, all in all, I think there's a fair amount of evidence that IUPAC currently leans towards using the name 'water'. There isn't an unambiguously clear decision yet, but the last quoted paragraph hints that a decision may be made in the next update of the Red Book.

The reason why 'oxidane' is needed is because names of polynuclear hydrides (e.g. HO-O-O-OH) as well as derivatives of water (e.g. O=N-O-N=O) are formally derived from 'oxidane'. Plus, as I outlined in another comment in this thread, 'oxidane' isn't actually an official name for water and if anything 'water' seems to be favoured by IUPAC. IUPAC rules can sometimes be silly, but IMO this isn't a great example of it, especially when said rule doesn't really exist to begin with.

From the IUPAC Principles of Chemical Nomenclature (1998): @http://web.archive.org/web/20110...:

The ending -ane signifies that the element exhibits its standard bonding number (i.e. the conventional number of electron-pair bonds), namely 3 for simple boron hydrides, 4 for the Group 14 elements, 3 for Group 15 elements and 2 for Group 16 elements.

Examples of this include:
BH3$B{H}_3$ = Borane
SiH4$Si{H}_4$ = Silane
PH3$P{H}_3$ = Phosphane
SH2$S{H}_2$ = Sulfane

As H2O$H_{2}O$ can be considered a hydride of oxygen, i.e. OH2$O{H}_2$, it receives the name oxidane:

Several of the names for the parent hydrides, although systematic, are not in general use, and...