Because "while 1:" is valid Python, but "while true:" is not ;) (gotta capitalize "True").

In addition to the GP's self deprecating sibling comment, I started using Python around 2.2, before there were even "True" and "False". So, seeing a 'while 1' loop is perfectly natural to me. But, I'm also perfectly comfortable with Python's "truthiness" in more places than most people are.

As a bonus: consider "while 'false' :" as a perfectly valid start to an unbounded loop.