You ask a huge question, which is discussed every day all around the internet.
But to take a high level stab at it:
Marketing is crucial to an early-stage hardware startup to start to determine if anyone actually wants to buy what you're proposing to build. Good luck getting money from a VC, much less a customer, if you can't talk intelligently about your target market, and demonstrate an ability to connect with it.
Sales becomes paramount after Version 1.0 is released, when you have to demonstrate that your business is actually profitable. Many engineers are under the impression that, if the quality is high enough, the product will sell itself. While this is true for the (tiny) subset of your market that cares enough to really investigate your product, it seems that a great sales team with a mediocre product will outsell a mediocre sales team with a great product more often than not.
It really depends on what it is you are producing, but in this particular case of the JooJoo/Crunchpad/whatever marketing and sales is probably part of the fundamental strategy. If a lot of time and money has been invested in something, it would be a major oversight to not have somebody who can specialize in distribution/marketing.