For web merchants (for example Qantas ticketing etc.) the email is just assumed to be good. If they have issues the customer will contact them via a call with an order ref.
They avoid the activation of email so they do not slow down the purchase flow. (same as we do on www.discourse.org/buy)
Assume its the same issue for @plkap74 when people spend 800 bucks on X-Carve