As far as I know, these were mostly for royalty and upper class. They have been found only in the tombs of those who were known to have high levels of social stature.
There are many things unknown about ancient Egypt and I believe that they were far more advance than what we accept them as today. There is some evidence of advance tools although much has been lost to time.
As for parasites, while they are more complex, a healthy body can be effective at avoiding infection.