Which wouldn't be a problem if the position had some real benefit. All tanks have weakpoints in their armor that are usually occupied by optics, radio ports, sensors, etc. You simply have to do this if you want your tank to perform its job effectively. The Germans and French tried very hard to cut back on vulnerabilities in the armor of their tanks and resulting vehicles usually had serious problems in situational awareness and maintenance.
A light machine gun in a blind position deterring attacks to a section of a tank infantry are already unlikely to attack? Not worth the vulnerability.