This is probably the only time I'll ever defend EA. They changed this after '14 because there were people trading and hoarding pucks and turning it into a business where they were making money by selling pucks for real cash! EA has made it clear this is cheating whether you sell or buy pucks and you can be subjected to penalties to your account.
This was issued shortly before the release of NHL 15:
https://www.easports.com/nhl/news/20...ling-or-buying
Unfortunately this hasn't slow down the people who continue to offer "pucks for cash". Logic would dictate that were headed to a no-puck trading allowed or a limited puck trading (similar to a pro league having to approve trades).
I too use to employ the system of using my reward pucks to help complete other collections. Unfortunately this is the dark side of gaming where users are more into profiting and exploiting as oppose to just enjoying what they have.