I think a lot of people who apply to schools pick schools that fall in their range, which they like from a glance and/or could see themselves at...It's often really hard to gauge how competitive you are as an applicant so while a student might've loved CU, they could've gotten into another school with a better package? Or even if there is no aid at the other school, they could've liked it more of felt that the high tuition wasn't worth it to them based on their present options.
Also, this process is so unpredictable, it's hard to predict who will give you an interview and an A, so you do have to apply broadly while asking if you can see yourself there. Then if you get multiple A's, you gotta seriously consider the tangibles: COA, educational quality, program/location, your happiness, etc...and at the end of the day people are gonna base their options on what they know so while someone might've liked a school, a high COA is enough of a reason for them to choose a lower COA acceptance, as long as they're still happy and can see themselves there