FWIW, according to CMT.com, the only women who are in the Country Music Hall of Fame (listed here along with their induction dates) are:

1970 Original Carter Family (including, of course, women and men
1973 Patsy Cline
1975 Minnie Pearl
1976 Kitty Wells
1980 Connie B. Gay
1988 Loretta Lynn
1991 Felice (and Boudleaux) Bryant
1995 Jo Walker-Meador
1997 Brenda Lee
1997 Cindy Walker
1998 Tammy Wynette
1999 Dolly Parton

In view of this information, now I really do wonder why Shania Twain was ranked above Maybelle Carter, and  Faith Hill, and several others were ranked higher than t Maybelle as well as Minnie Pearl, Cindy Walker, Brenda Lee, and others in the CMHF.

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When it comes to looks, I still don't think they are nearly as much a prerequisite for commercial success for male c/w singers as for females. Roy Clark, Charlie Daniels, Hank Williams Jr., George Jones, Lyle Lovett, Willie Nelson, etc., are hardly leading man types. Even Garth Brooks describes himself as "a little fat guy with a baby face" (or words to that effect). The women, even if they don't have movie star faces, usually have that slender, not-too-pear-shaped figure and are either under forty or look like they are (ah, the wonders of plastic surgery).

In other genres, you have/had Ella Fitzgerald, Patti Lupone, Pearl Bailey, Kate Smith, Mama Cass Elliott, Janis Joplin, Rosemary Clooney (even after she got fat), Bette Midler, Joan Sutherland, Aretha Franklin, and a slew of others who lasted beyond their youth, are/were far from the fashion model shape, and/or did not have what the general public seems to consider "pretty" faces.

But maybe it's not just c/w -- maybe the proliferation of music videos in most genres has begun to make looks way too important in most types of commercial music.