In the UK you won't get to be a professor until your forties, and many people never do.
Here professor is quite a distinguished title, and while it isn't legally protected, I've never seen it used for anyone except a very senior academic who has been formally appointed as a professor.
https://people.eecs.berkeley.edu/~bh/
who designed and then taught the introductory computer science course (CS 61A) for many years and is now retired.
The percentage of Ph.D. graduates who took North American
academic jobs rose in 2015-16 for the second straight year,
to 30.7 from 29.0 last year. However, the percentage of
graduates taking tenure-track positions in North American
doctoral-granting computing departments fell from to 10.0 in
2014-15 to 9.0 in 2015-16. The percentage taking positions in
North American non-Ph.D.-granting computing departments
fell from 2.3 percent to 1.6 percent, while the percentage
taking North American academic postdoctoral positions
jumped from 9.7 percent to 14.3 percent.[1]
[1] https://cra.org/crn/wp-content/uploads/sites/7/2017/05/2016-...2002-2003 Senior Researcher, Intel Research (Berkeley)
2003-2011 Harvard
according to his latest webpage at http://www.mdw.la/
Harvard University School of Engineering and Applied Sciences
Gordon McKay Professor of Computer Science
July 1, 2010 July 1, 2011
Harvard University School of Engineering and Applied Sciences
Thomas D. Cabot Associate Professor of Computer Science
July 1, 2007 June 30, 2010
Harvard University School of Engineering and Applied Sciences
Assistant Professor of Computer Science
July 1, 2003 June 30, 2007
Intel Research, Berkeley
Senior Researcher
August 2002 July 2003