They're lint free and pick up any small particles or grime that might have been on the fingers of the last person to install the cable.
[There have] been numerous accounts of techs in the field who had a greasy lunch and the install directly after didn't run as smoothly as it should. Although this didn't fix our problem (we had a bad ethernet cable) he claimed its worked wonders for tons of other, now satisfied customers.
Ever tried this tactic? Leave your experience in TalkBack.