The verse that Master Dogen valued so much on donning the robe (or Rakusu) which we can receive is (translated of course):
How great is the clothing of liberation,
formless, field of happiness, robe!
Devoutly wearing the tathgata's teaching,
Widely I will save living beings.
We adopt the robe to drop everything, to 'wear' the formless field of happiness for everyone. Its just our practice itself. We don't need it to practice of course.
I personally feel that wearing the robe in this way (per the verse above) was/is more of a challenge to my cherished identities than not wearing it was. Also, I feel that my wearing the robe contributes in some way to transmitting the practice into the future.
Sure, it feels all nice and 'buddhisty' sometimes, but that soon wears off when our knees and ass get numb!
The robe is the transmitted Buddha-Dharma,
The robe is just a piece of cloth,
The robe is our Buddhist Practice,
The robe is just this amazing and terrible Reality itself.