This was part of a broader pattern through the 19th and 20th centuries of inadequate female facilities. 'Respectable' women couldn't relieve themselves in 'retired streets' or alleys as men did, and the few toilets available in Victorian London were overwhelmingly built for men. Women who wished to travel into central London or even further for leisure and pleasure had to carefully plan where they could ‘stop off’, en route to their destination. Thus excursions outside the house were often based on visiting friends and family, where toilet facilities could be guaranteed.
Lack of access to toilets effectively tied women to their homes, putting them on a leash as long as their bladder capacity. Even when London's first public toilets were built for the 1851 Great Exhibition, the prevailing modesty of Victorian society assumed women would be too embarrassed to be seen entering them.
This was part of a broader Victorian pattern of dividing the city into a male-oriented 'public' sphere and a female-oriented 'private' one. Victorian society saw the ideal woman as being 'the angel of the house', naturally focused on being a good wife, mother, sister and daughter. From the mid-19th century, workplaces, railway carriages, even banks were often gender-segregated. Smaller, more cosily-decorated spaces were cordoned off for ladies to protect the 'weaker sex' from contact with the masculine world of business and public pleasure.
This silent discrimination still continues in many countries around the world. As recently as 2012, female demonstrators in India marked International Women's Day by storming men's public toilets in the city of Nagpur, protesting inadequate numbers of bathrooms for women.