Only in exactly the same way that being in SERPs was important 5 years ago.
It's definitely important to be in both, though one needs to evaluate the limitations and ROI of each platform. At least here in the USA, I'm not seeing much value in spending a great deal of time, effort and money in organic SEO or paid ads for that matter. Google is burying the specialized sellers and service providers well below big brands and Google's other properties/services. And those that care enough to go into detail about their products and services (getting to Editorial Guy's point), the answers to those questions may be lifted (direct or indirectly) by Google and further diminish the value of traffic. What I mean by diminished traffic value, is a time when a potential customer would once find a comprehensive answer to their question on our site and say "this company really knows their stuff so I'm going to buy from them" and instead the answer is provided to them by Google and the sale or at least the positive impression we left with the potential customer is lost. And while we can restrict Google from using our detailed answers in the knowledge box, those that scrape and post our stolen content (sometimes reworded/spun) are not controlled by us.
Right now, the question for retailers is "how is Google trying to eat your lunch"
Here in the USA, there is only an appetizer for Google to eat. Most USA shoppers have left search engines and Google being the largest among them has lost the most. That's why I feel that what little buyer traffic they get is being rotated to different sites. This also helps to explain why our conversion rate from Google is so poor and why we get bursts of sales from Google between prolonged periods of time when Google appears dead. If Google quit rotating the buyer traffic, and dropped the domain crowding, it may add value to being ranked #1 instead of the current moving target that leaves Google traffic with half the conversion rate of Bing and Yahoo. Regardless, there's a lot of data that supports far more purchases involve an interaction with Amazon than search engines - leaving Google with much less influence over product sales. The proof is in the numbers for me. Though we are not yet halfway into July, my total sales are forecast to be 25-30% greater than they were in July of 2016. This is without wasting time, effort and money with Google (SEO or Adwords).
Amazon is not your friend. Even less than Google.
Friend or foe, USA shoppers are spending a lot of time and money at Amazon. Ones failure to be found where these shoppers are spending their money at is more detrimental to sales in the present than what may or may not happen down the road. I know there's a lot of American businesses still stepping over earning a dollar on Amazon to pick up a dime on Google, which is good for those that adapt to changing buyer habits and are able to reach a larger percentage of the buyer market. I don't see Amazon or Google as my friend, but I do see where sales are coming from. And few are coming from Google even though my site ranks really well. But ranking really well means little when Google buries pages beneath the fold, often because of domain crowding, and rotates what little high buyer intent traffic they have.
being found in Amazon is important
Not to me.
Which is good, and let's hope it stays that way. Though my guess is you feel this way because you reside in and serve the UK market. Just as Google personalizes search results, they can and do use different data sets and tweaked layouts for different geographic regions in large part to accommodate political and regulatory pressures. Having a stronger regulatory environment in the UK likely has its benefits when it comes to protecting the interests of consumers and smaller enterprises, which you are a benefactor of. Regardless, I don't live in a bubble. I realize government policies in different regions influence those regions differently and the perceptions of those operating within totally different environments. Unfortunately there's not much interest here in the USA to restrain big search, social and marketplaces. Though it's my hope that at least some of the regulatory actions taken in the UK to hold big search, social and marketplaces accountable can be used as a model in other regions throughout the world including the USA.