It never occurred to me check to see if it had it before buying, because for years integrated SXM (with antenna) has become so ubiquitous in most car models sold in the US. It probably wouldn't have single-handedly kept me from buying a Gravity, but it has been a frustrating compromise to overcome. I know many people don't use SXM and don't see the big deal, but for those of us that do, the convenience of having 100+ channels of consistent, dependable content (other than going through a long tunnel or through a tight mountain canyon with tall walls, which is rare and very short) is a big deal to lose when AT&T cell service sucks and the car's native audio streaming systems are frequently cutting in and out.
AT&T sucks in my local area (and it's not like I live in remote Alaska, this is just north of Denver). And when it does cut out, sometimes it never reconnects for the rest of the drive (that's more than a dead zone problem). And even when there is a signal, the car's Spotify app freezes on ads. It was just one frustration after another trying to work around this to get basic, dependable audio without an integrated SXM antenna. Eventually Android Auto came to the rescue. It's not the ideal solution, and it still cuts out on some long road trips routes because even my phone's much better cell service has occasional dead zones in remote areas, but it's 10x more dependable than it was before AA.
So many compromises with this car. It does a lot of the hard stuff really well. But the easy stuff is often so frustrating.