I understand that there may be a need for some grooming if one goes from a long flight into a meeting. However, shaving in a lav is to be preferred over doing it in the aisle.
Lounges such as IST and TPE allow one to have showers, shave, and change clothes. That has been my personal preference and why I carry the needed items for that in my carry-on.
Do a YYZ/YUL - IST - SIN without, and you're wearing the same clothes for 3 days...