Rule of Backpacking: Ounces matter. Ounces add up to pounds.
Ounces equal pounds; pounds equal pain.
Honestly, I wouldn't take a shaving kit while backpacking. If you are out for a week, no big deal. That shave when you get off the trail is luxurious. If you are out for longer than that, you'll be going into town to resupply so take care of it then. Either send some stuff to yourself and/or bounce it forward to the next town. Or just grab an orange Bic and take care of it in a Walmart bathroom.
If you did take a shaving kit into the backcountry, it's just more stuff to go into the bear bag at night. It's not worth it to me. But we all have our luxury items we bring.