Galaxy series from S6 have very fragile back. It can be easily broken from a small drop. I had Galaxy S6 for some time and I have changed back Glass four times. Four Times! Yes and recently my S8 phone back also got cracks from a minor drop.
I know that Samsung is using Glass to support Wireless Charging but don’t know why they are not using Gorilla Glass or similar stuff to make it strong. It only takes one slip and boom. You got a crack.
While I was searching used phones on classified sites. I have seen the most of the owners mentioning that back glass is broken or cracked. Samsung should do something about it.
To make matter worse, these phones are made of total glass which made them too slippery. It’s very easy to get the dropped from your hands.
My conclusion is that you can’t use these phones without military Grade cover.