Oh yeah, something else- manufacturers generally tend not to make claims that their helmets are "safer" (though again, with new technologies such as Wavecell, some have begun to make such claims). Doing so would open them up to litigation. So typically they tell you that all of the helmets sold meet federal standards and therefore are equally safe. However, objective testing (i.e., Virginia Tech) shows that that isn't precisely true.

A problem with this legalistic approach is that if all they will say is "meets federal standards", then there is no motivation for the manufacturers to innovate and improve helmet safety. But again, with MIPS and other newer technologies, this logjam seems to have broken and manufacturers do now strive to improve safety.

Also, I think the existence of independent safety tests has put some pressure on them to improve. The "safest" scores on the Virginia Tech site have diminished in the last few years.