Last year my friend and I were bridesmaids for each other, in weddings roughly six months apart. Aside from having been friends since childhood, in the year leading up to our weddings, we had each gone through deeply traumatic losses.
We were uniquely able to support each other - had it not been for her I may well still be sitting in my room, as I was the night before, having a major meltdown which my husband, as loving, gentle and empathetic as he is, had absolutely no clue how to get me out of.
Our weddings were very different, but each in their own way distinctly unconventional. Perhaps partly because of the rough times we had been through, we and our now-husbands didn't hesitate to dispense with traditions that didn't work for us, including but not limited to bridesmaid-related traditions (we each chose our own dresses, by the way, and certainly didn't follow each other around all day).
On the day, and leading up to it, we both needed each other in a capacity that was distinct from being friends: other friends did readings, but we needed each other in the 'wedding party' (a phrase I really don't like). We made the walk with each other, and gave a speech for each other. There was nothing 'little girly' about the roles we performed: speaking for myself, it felt like a tremendous responsibility and one of the most 'grown-up' things I've ever done.
OP you may not have needed a bridesmaid, but that doesn't mean that other women don't, or that their need can be described as 'silly'.