It is really difficult to get into BYU right now. The caliber of student enrolled at BYU currently is very high level academically. And for the most part, the goal of many undergraduate students is to get into grad school. Despite this competitiveness BYU still doesn't have the name reputation of a Stanford or Harvard. So why would professors hurt the future grad school prospects of many highly qualified students by giving them lower grades? It seems like grading on a curve at a school like BYU with its overall level of student would discourage students from enrolling.
I actually have a nephew who chose to accept the Presidents Scholarship at UVU over BYU because he thinks it is better for his long term prospects. He can attend UVU, have everything paid for, and leave with a likely 4.0 GPA and access to pretty much any grad school he wants to attend in the future. And by living in Orem he can still be part of the BYU social scene as an active LDS kid. Its all the more disappointing because he is Hispanic, and demographics is one area that is currently hurting BYU's overall rating as a university.
I'm not saying professors should artificially inflate students' grades. But giving a kid a 'B' when he has done 'A' caliber work simply because he or she is competing with 'A+' level work on a curve seems like it only benefits the ego of the professor.