I just don't buy Jane Wyman as a glamour girl

I don't understand why the studio continually put Jane Wyman in glamour girl parts that clearly did not suit her. Here she is a model, and David Niven is bowled over by her in their first scene and can't stop looking her over - it's played like he can't take his eyes off her. But it doesn't fit = she's not Lana Turner or Ava Gardner. But she got lots of roles like this - In Three Guys Named Mike she plays a stewardess (at age 34) who is pursued by three guys, who ignore her stewardess roommates, who are younger and arguably prettier than her, and only pursue Wyman.

I buy her much more in a part like Johnny Belinda, in which she was wonderful.