It doesn't work that way. The reality is that students are used to being in school from about 8 to 3. They tend to resist taking classes much past that time, and by college, they tend to resist taking classes before 10 as well.
The tendency to not treat college students like adults and accommodate for this behavior with more wasteful behavior by the schools is yet another factor which attributes to higher costs. If that same student started working instead of going to college, their boss would not care that they are used to working 8-3. Colleges shouldn't care either.
And it isn't just momentum, either. Lots of students commute to their university, which means early and late classes don't work. Parents (both college students and faculty) have to pick their kids up from school. Students have part-time jobs to pay the bills. And so on.
Everything you said here is the same for a working adult, so no extra accommodation is necessary for an adult student.
Finally, it isn't practical to just say, "We're going to spread classes evenly throughout the day", because students need time to actually work on their homework. And that time needs to be during the day so that they can use campus facilities such as computer labs, tutoring centers, etc.
Spreading classes evenly throughout the day is not the same as saying every student has classes from 8-5. Students with 15 credit hours will still only spend about 15 hours per week in class, leaving plenty of time to hit the library or computer labs.