You learn to fly by memory actions, checklists are there to trap items that if missed could be a real hazard to aviation. If you try to learn them, then miss a single item because of a minor distraction, then what?
I made up my own checklists based on the POH but removing trivia that doesn't affect flight safety (eg radio master on) and would be immediately apparent if I forgot.
Other items, eg fuel management etc are so important that committing a checklist to memory is a sure way to forget. Airlines don't expect their pilots to memorise checklists, so why try?
One of the other hazards is as you become familiar reading a checklist on a regular airplane, you tend not to actually read/do the items but skim over them. Again, another potential trap. Use a checklist and use it with rigour to trap any mistakes. This could save your life.