Of course not, but there is a degree of proportionality here. In theory a person's personal diary, letters, chequebook etc could contain evidence of crimes. However it's generally not been considered appropriate to read through them during a customs search.

The rights granted under the constitution were provided explicitly under the knowing assumption that they could be used to conceal actual crimes or criminal intent. That's the point of them needing protection from the authorities. The mere possibility of committing a crime isn't enough grounds to invade a person's privacy to that degree. You need actual reason to suspect it in an individual case to go that far.