This can also be a side effect of narcotic medications.
So … what’s up with dogs that never howl?
They don’t have the howling gene. 
Or, they’ve never been around other howling dogs. Or the vocal trait hasn’t been selected for.
Howling/vocalizing is partly breed-specific. Some dogs are bred for hunting “voice”, like some hounds and tracking dogs. Others, like malamutes and huskies already mentioned, seem to have more wolfy traits and are vocal. And some dogs (like Basenjis and sight hounds - being vocal wouldn’t be adaptive behaviour for sighthounds) are really quiet dogs.
Ours don’t really howl, although Sadie (a mix, probably American Staffordshire Terrier/Basset Hound/maybe Beagle) definitely makes roo-ROO-roo-roo vocalizations when she’s sufficiently excited.
Simone (American Pit Bull Terrier) doesn’t, but unlike Sadie, Simone pays a lot of attention to electronic noises (phones, vacuums, and especially the TV) so I think she must be aware of sirens.
Both of them routinely bark and ROO like crazy when the foxes scream at night in the woods behind our place. Of course, fox screams can be pretty unsettling for humans too – I hear they’re routinely mistaken for the screams of human children, and I find the sound pretty creepy myself.