Assuming your username means you're in college: I would wait for a few more years before appointing yourself the expert on other peoples sleep physiology. It's easy to think this way in college because people around you will be sleeping poorly or erratically, won't respect sleep or bother with sleep hygiene.

Once everyone is out of college the biological differences become a bit more noticeable. Most people will "fix" their sleeping relatively easily. Others will struggle at first but eventually make it work by adopting strict sleep hygiene and routine. Then a few will find that no amount of sleep hygiene gets them into a good cycle for the standard working day. For some of them the issue will be severe enough to qualify as a clinical disorder like DSPD. DSPD is known to be extremely difficult to treat.