根据以下内容回答题：As late as l800．women’s only place was in the home．The idea of women in the businessworld was unthinkable．N0“nice’’woman would dream of entering what was strictly a“man’s wodd”．Even if she could，what would she do?Men were positive that no woman could handle a job outside her home．This was such a widely accepted idea that when the famous Bronte sisters began writing books．in 1 846，they disguised themselves by signing their books with men’s names． Teaching was the first profession open to women soon after l 800．But even that was not an easy profession for women to enter because most high schools and colleges were open only to men．Oberling College in Ohio was the first college in America to accept women． Hospital nursing became respectable work for women only after Florence Nightingale became famous．Because she was a wealthy and cultured woman，as well as a nurse，people began to believe it was possible for women to nurse the sick and still be“ladies”．Miss Night-ingale opened England’s first training school for nurses in 1860． The invention of the typewriter in 1 867 helped to bring women out of the home and into the business world．Because women had slender，quick fingers，they learned to operate typewriters quickly and well．Businessmen found that they had to hire women for this new kind of work． By l 900，thousands of women were working at real，jobs in schools，hospitals，and officesin both England and America．Some women even managed to become doctors or lawyers．The idea that“nice”women could work in the business world had been accepted．

Bronte sisters published their first books under men’s names because__________ ．