Hc, the witnesses have to state that they signed in each other's presence and in the presence of the testator,for one thing ! And nobody puts "being of sound mind" in a will, if they ever did in England, because it would be self-serving statement which does not prove itself ; a person of unsound mind could put that; and it doesn't serve to prevent the will be challenged for lack of testamentary capacity.And, for the avoidance of doubt, it is customary to put "and I hereby revoke all wills and testamentary dispositions made by me", or similar words, after "last will and testament"