Thugs and thieves use walk through transoms to board a boat silently during the night. They're great for access to the water but that also makes for a target in an anchorage. As much as we like a walk through or sugarscoop transom we feel much more secure in our 'high freeboard' boat. Thieve swimmers will target more easily boarded vessels as it's impossible to board ours from the water.
Sounds paranoid I know but we've had friends boarded, beat up and robbed in two different instances. It's a jungle out there and you need to protect your security. Walk through transoms are counter to that concept even though we like them.