What benefit do you get from spending £30k on a new car or £10k on a holiday to somewhere sunny? The benefit is what is MEANS to you, you can't rationalise something like that.
Clearly your fiance sees marriage as a sign of commitment and love between two people - something that it appears (at least to her) you're not willing to offer her.
Ermm, I'm not the OP. I'm not engaged, think some people are getting confused here. I'm just trying to work out why some people are so dead set on marriage, and why they feel they need to pressurize others into this archaic institution, despite there being no real reason to.
I still don't understand why anyone would need to end a perfectly good, happy, working relationship because of not getting married?