The problem for the manufacturer comes when consumers figure out that they can use knock-off blades, generic ink, or 3rd party juice packs.
'Juicero’s business plan reads like a pitch-perfect parody of contemporary startup culture. One investor told Bloomberg that Juicero was building a “platform” for a new model of food delivery. ...The technology is mostly superfluous from the customer’s perspective. But the technology dimension was crucial for fundraising. As one investor put it to Bloomberg, “Their venture firm wouldn’t have met with [Juicero founder Doug] Evans if he were hawking bags of juice that didn’t require high-priced hardware.”'
Gillette model worked because creating that infrastructure back then had a huge barrier to entry. You had to get a factory to produce the blades, etc.
Compare that to juice mix delivery service in 2017. There are tons of organic juice stores around, and there are tons of delivery services like uber/caviar/doordash. These juiceries can take advantage of the distribution startups to deliver their juice and make money if they wanted.
Basically it matters because you need to take "competition" into consideration. It's an entirely different game than razor blades.
Given the opportunity, how much of your own money would you invest?
This machine is expensive and the supplies are expensive. That... does not make sense. Given that the supplies seem to be delivered by means of some subscription service they'd have done better to throw in the machine for some nominal monthly cost - and make it free for those who manage to consume more than X bags of pulp per year. This also would lower the threshold for potential customers as it would be possible to try the 'service' without needing to invest a large sum up-front. Given that the money is meant to be in the bags it only makes sense to try to maximise the number of customers.
I guess they had a look at Apple and thought their business model - expensive hardware tied to a single supplier in as many ways as possible - would fit them as well. It doesn't, not when you can pick actual apples from a tree in your garden.