Some details about the bride's look:
at this page about the wedding it says
To become Crown Princess of Norway, Miss Sonja Haraldsen designed herself a very simple and simultaneously very elegant wedding dress.
... which royal bride would probably do that nowadays?
In line with the tradition of Norwegian royal brides but differently from what was already a tradition in the rest of Europe, Miss Haraldsen did not wear a tiara on her wedding day, having only some discreet flowers on her hair.
So that's why also Ragnhild and Astrid didn't wear a tiara on their wedding days.