Nowadays many cities become similar as many people now have abilities to work in different countries and cities. I believe it is a negative development as people become less involved in local history.
Many architects and building companies now work in many countries, as their workers can easily visit the places for buildings and communicate with builders distantly. It became available with fast transports like planes and trains and the development of the Internet. Therefore companies can apply their Ideas in cities from the USA to Japan without significant changes. Consequently, cities become similar without special features in buildings and ideas in architecture.
With the trend of making cities similar to each other, cities lose their personalities as there becomes less and less styles and buildings, especially for one particular city or region. Therefore people become less interested in their culture and history, as they can probably find in every other city. Consequently, these people are likely to repeat the same mistakes as their ancestors in these cities, as they have not probably seen notions about it.
In conclusion, I believe that cities are becoming similar with the development of ways of communication, which leads to applying similar ideas in different points of the world. As a result, this similarity might lead to decrease of interest of people in local history and culture.