Manufacturers typically dictate reseller pricing and marketing to serve the needs of their brand ("you can't sell below x as that makes our product seem cheap") so dictating a sales tactic isn't unimaginable. Especially if the tactic is designed to sell services and what not the manufacturer offers via the resellers.

My other guess is that the resellers have figured out that while they cannot fleece you on the price of the device - they all sell the same, identical hardware after all - they can charge you extra for services, support insurance and extra options as long as those prices aren't readily available for comparison.