It's just a different approach.

Either you have wallet.dat file with private keys which you must hold in dark cold place, affraid of viruses, bad blocks and your mom cleaning room early morning. Or you have just long passphrase associated - in your brain olny! - with some good old times when grass was greener and light was brighter... oh, nevermind

Both ways have some weak points, both required to understand things, both give you good ability to lost everything you have.

And I not even speak about thermorectal cryptoanalysis!