I'm the Grandson of a Canadian Tanker from WWII, and I've been told by someone who was there that tankers did in fact exit their tanks, even in battle.
My Grandfather's tank had a track thrown after being hit in combat. Unable to move the tank, and unable to effectively do anything in the driver's seat, he bailed, and joined with a group of infantry men to protect the tank. (You don't try to repair a track under fire.) The rest of the crew remained to operate the weapons for a short time, eventually bailing themselves after the commander felt they were at too great of a risk due to the fact they were not in a good hull down position.
My Grandfather was apparently given the weapons and ammo of a wounded American GI, and they fought for the rest of the afternoon to secure their tank. That evening they repaired the track, and withdrew for further repairs and rearming.
Other times, they often got out of the tank just to look around and scout. Tanks are big, noisy, and attract a lot of attention. A dude crawling through some shrubbery isn't. Crewmen left the tank in the middle of battle to look around. Tanks are not easy to drive, they are not easy to see out of, and finding out that you can't actually fit somewhere in the middle of a battle sucks if you do it the hard way and get yourself stuck.
They commonly strapped weapons and spare small arms ammo to the hull of the tank. My grandfather apparently had even got his hands on an LMG that they made use of several times during the war while dismounted.