Hmm. That's news to me, though it is an obviously common misperception. The fact is, if it is properly constructed, your shower shouldn't leak even if there is no grout or caulk (though a lack of caulking or sealant could cause extensive water damage to the wall).
Going online, I entered the keyword phrase "water damage showers" in a search engine. In the first 20 hits I found 14 such references, many from similarly reputable companies. While the misconceptions are many, it is clear that water and vapor problems cause billions of dollars in damages every year, not to mention the latest star in the spotlight, mold damage.