Blimey, don't hold back ladies, will you?
I feel the same as the OP. My partner and I are actively trying for a baby, with no plans to get married at the moment. Horrors!
Legally and in terms of insurance etc, we'll make sure everything is in place. That is our business and we'll sort it. Unmarried parents do have the same rights as married couples, since 2003, providing the father registers the birth alongside the mother. We're not just bumbling into this blindly and will prepare accordindly.
I don't want/need to make a public declaration of love- private declarations suit me just fine. I don't get that argument at all. I don't need to declare anything publicly, least of all anything to do with my most personal relationship.
We have been together for years, and done the whole better/worse, sickness/health thing to the Nth degree. Friends of mine have met, married and separated in the time we've been together. The fact that we are still together and planning the next exciting stage in our life is celebration enough for me.
I never once gave a thought to my parents or my friends' parents being married or not when I was a kid. In fact, it only became relevant when my parents divorced.
We will probably get married one day, but it frustrates me that once we do get pregnant, we'll have to spend hours defending ourselves. (My brother actually said "you can't have a baby before you're married? What will Granny say?!"). And, frankly, I'm not spending thousands of pounds, or even caving to pressure to have a quickie cheapo ceremony, just fend off this type of pressure.
So no. You are not being unreasonable, IMO.