Instant plants! (Just add tachyons)

Why is it that every time I'm asked about what would be a good vine/hedge for a privacy screen (invariably in shady or very dry spots), the person becomes visibly disillusioned when they discover it'll take "a couple of years" to actually establish it? What were they expecting, 14 feet in three weeks?

"I'm sorry, sir, no one sells Ultra-Vigorous Drought-Resistant Non-Invasive Kudzu."