A lot of people like to use the phrase "is comprised of" -— about 136 million of them, if a recent Google search is any indication.
"Houston is comprised of many neighborhoods," one website tells me. "Workforce planning is comprised of a number of key tasks," another insists. And, my favorite, "Erythrocyte spectrin is comprised of many homologous triple helical segments." (Like we didn't know that already.)
Skimming through all these uses of "comprised of" supports my longtime suspicion that people use this phrase when they're trying to sound official, formal or informed. There's nothing wrong with striking a formal tone in contexts that call for it. In academic writing and some business writing, formal language is requisite. (It's also handy when arguing politics with hardheaded, uninformed relatives. But it's too early to start planning for the holidays just yet.)