So you have "faith" that the assumed physical constants that were used to calculate how thick those cables needed to be really are "constants"?
Yes. Why not? For now, in this world as it exists now, it's been demonstrated to be reliable, although accidents do happen and some elevators fail.
Don't you have faith that constants have been what they are for millions of years?
Don't you believe that radioactive decay has always been what it is now? Based on what?