When Python3 came out in 2009, it was already heavily debated. Python3 would be incompatible with previous versions of the popular language, but fix many drawbacks. While the vision was clear and the community initially planned to move forward much quicker. The demand for having a 2.x branch was so huge, however, that the community decided to extend support for 2.7 until the end of 2019. Stack Overflow took a look on why the path took so long.