One of the earliest notorious all-women bands is Fanny. Joan Jett's first group the Runaways were also an early famous all-women band. One of the strangest is undoubtedly the Shaggs, a group of sisters with limited mastery of their instruments as well as song structures, who have a cult following. Punk and its acceptance of very limited musical skills opened the door wider for women with a desire to rock, spawning groups such as the Raincoats, the Slits, and Lilliput. Some well known all-women bands had men in the band at times, particularly but not limited to drummers.
All-women bands exist for different reasons--some as a feminist political statement, some, such as the Go-Gos more for novelty. Audiences will show up to see an all-women band simply to see if they can actually play. Sometimes women form their own bands due to the limitations of male domination in the music industry in general. Women who want artistic control sometimes form all-women bands as a way to reduce challenges to their authority. Certainly all-women bands are still considered novel, and have a certain appeal as an alternative to all-men bands and the male perspective.
Courtney Love, leader of the almost-all-women band Hole, has said that it's impossible to find a female bass guitarist for your all-women band. This is belied by her own former bassist Melissa Auf Der Maur and the hot female bassist from the movie School of Rock. She recently (2003) took out full-page ads in rock publications seeking the elusive female bassist.