At my job I get to see students' transcripts and sometimes students lose credits because they can transfer at most 64 credits from 2 year colleges. Why would a student take more than 64 credits at a 2 year college in the first place?
Where I work registration must be advisor approved, but plenty of incorrect registration gets approved and happens anyway, so I expect you're right some of the time.
Maybe some of them start out with the goal of an associates' degree and then decide they want to finish out a bachelor's at a 4-year school...
One of the things I advised students to do (as a former youth pastor) when they first went to CC/JC was to explore a bunch of different areas if they didn't really know what they wanted to do or even study. A big part of the reasoning is because it's so much cheaper at that level to try a significant variety of courses and fields. Figure it out there, and then push towards the Associate's and potential Bachelor's degree even if it means some credits don't transfer.