What was also bad (and unforently is becoming a trend) is showing stuff in the E3 demo and totally removing it from the final product.
If you read that "Final Hours of HL2" from GameSpot / Spy / Wherever (can't be arsed to find a link) you'll find that explained. The E3 HL2 demo was made as a "proof of concept" once the Source Engine was stable(ish) and was designed as a document by the designers to show Gabe et al what they wanted to do with the game. So they made a series of short sections (The Strider, the following Antlions in Nova-Prospekt etc) to show how they intended to use the engine. But inevitably with designing a complex project, bits get edited, changed and chopped out. Ask anyone that does serious mapping (or read Dave Johnston's story behind the creation of de_dust) and you'll see how organic mapping and designing content for games is.
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We don't go to Ravenholm.