Being able to mount and unmounts tyres without levers is always a great skill to have, but regardless of whether you can or cannot do it, I always advocate carrying a tyre lever out in the field as a precaution/insurance. You never know when you've punctured in the middle of nowhere during a long ride, and your hands are all tired and hurting for some reason or other -- changing a tyre in the comforts of your home/garage/bike shop can sometimes be a lot different from doing it out on the road while tired/hurting/wet/rushing to meet a cutoff/whatever.
If you can still do it out in the field under adverse conditions, that's awesome. But if for some reason or other you're unable to... well, at least falling back to using a tyre lever is better than being stuck in the middle of nowhere.
Last edited by atwl77; 10-02-19 at 09:41 PM.