The gist is essentially that Apple Music subscribers who like a single can just add it to their library and never have to buy it and that it could mean the charts begin to die. Or at least, I think that's what they're saying.
Buying a single now means one of three things, none of which have an immediate impact on our own listening.
A) You want to help the song climb the charts. The Official Charts (and now, it seems, the iTunes chart) are still heavily weighted in favour of purchased songs. The Official Charts count one ‘sale’ for every 100 streams. (To be fair this has long been true of teenagers who wouldn’t dream of actually spending money on music for any other reason – throwing some cash at a download means the same as spending money voting in a TV singing contest.)
B) You want an artist – or a label, or a songwriter, or a producer – to have some money. In this case, buying a song is similar to making a donation. Almost a donation to charity, really.
C) You don’t really trust music streaming – what if a song suddenly disappears one day during some sort of royalties dispute?
Obviously it's an Apple-centric piece because I assume this has been the case for anyone with a Google Music account, Spotify Premium, etc. for a while. Or maybe that's valid because single sales on iTunes are the big online sales point.
This isn't on the Music board because those guys are boring.