Comment 92 for bug 1357093

For those still having this issue on Ubuntu 16.04 : please check that you did not disable the automatic installation of updates.
It might be the reason why the old kernels were not removed for me (not 100% yet). See discussion in https://ubuntuforums.org/showthread.php?t=2344232
With a GUI, it's in System settings->Software and updates->Updates tab : "When there are security updates" should be set to "Download and install automatically" (its default value).
(please comment on the forum thread)