Map categorization query

[TargetPractice]

Why do Quake maps seem to be categorized by the textures used within them? I've seen categories such as 'metal maps', 'base maps', and the like, with the textures used apparently being the major discriminating feature. Is there an specific reason for this, or did I just miss a common Q1 design convention?

[Sajt]

Where are they categorized by this?

The texture themes are generally a way to make some continuity in an episode, i.e. have a series of similar themed metal maps, etc.

[scar3crow]

Its also noteworthy that each level kind of has its own designer. Though not completely true, e2 is mostly Romero, e3 is more McGee and e4 is all Peterson. e1 represents several styles and thus has its own feel (best mimicked by Beyond Belief), and consequently has several people who worked on it.

Referring to them as such just makes for a quick reference, as it theoretically also implies certain conventions (metal maps generally have lava and more deadly traps and are very tight, medieval maps usually use the waters and nail shooters for traps, base is obvious and may use slime along with laser shooters, so on, so forth).