PlayStation Store on PS3 will close in select markets starting this year, followed by global closures for PS3 and PS Vita next year. That means new content purchases will no longer be possible once the PlayStation Store closes on these devices. To ease the transition, players will still be able to download previously purchased content after the closing date for the foreseeable future.
This might not be as big a news article as people claim, though I see how it can feel that way amid the disc closure announcement.
If they do it like some systems, you might be able to open a web browser to make the purchase, and then download it on the system. When it’s happened before (I forget which system), the main reason was simply that the device didn’t support newer HTTPS connections for payment info.