Salt Lake City will always be considered "smaller" because of the fact they didn't go "annexation crazy" (for useable land) like other cities did.
Another thing that uniquely affects our population density is a good portion includes undevelopable land (government owned, terrain, etc.). Salt Lake City's useable land is probably closer to 60 sq mi; geographically much smaller than most other cities (which, if adjusted, would nearly double its density).
Some comparisons: (listed in order of a city's square miles)
Los Angeles: 469 sq mi, pop. density 8,225/sq mi
MSA: 4,850 sq mi, pop. density 2,645/sq mi
New York City: 302.64 sq mi, pop. density 27,550/sq mi
MSA: 13,318 sq mi, pop. density 1,876/sq mi
Chicago: 234.0 sq mi, pop. density 11,864/sq mi
MSA: 10,874 sq mi, pop. density 1,318/sq mi
Denver: 154.9 sq mi, pop. density 4,044/sq mi
MSA: 8,414.4 sq mi, pop. density 314/sq mi
Las Vegas: 135 sq mi, pop. density 4,298/sq mi
MSA: 7,910 sq mi, pop. density 247/sq mi
Philadelphia: 134 sq mi, pop. density 11,379/sq mi
MSA: 5,118 sq mi, pop density 1,138/sq.mi
Salt Lake City: 110 sq mi, pop. density 1,666/sq mi
MSA: 9,555 sq mi, pop. density 119/sq mi
SL County: 742 sq mi, pop. density 1,396/sq mi
Boston: 90 sq mi, pop. density 12,900/sq mi
MSA: 4,674 sq mi, pop. density 947/sq mi
Washington DC: 68 sq mi, pop. density 10,528/sq mi
MSA: 5,564 sq mi, pop. density 963/sq mi
As you know, the Salt Lake MSA includes Salt Lake, Tooele and Summit counties—the latter two being geographically much larger, very rural, and mostly government owned. Our MSA will
NEVER reach the density of other MSAs for this very reason.
I wonder what Utah's density would be if we excluded ALL of the government owned land in the state—since it will never be possible for it to be developed.
As you can see, it's possible to tweak any statistic to skew numbers into your favor.
On another note:
Las Vegas is only as big as it is because of
ONE industry—🞵🞵🞵🞵🞵🞵🞵🞵. Take that away and it would be comparable to Barstow—or smaller. The tourist and convention industry would not exist as it is. If for some reason, Las Vegas were to lose 🞵🞵🞵🞵🞵🞵🞵🞵, without question the valley would become the largest ghost town that ever existed.

What other city in the world has created such a size, and continues to exist because of only one industry?