I suspect the bridge forward is as much an evolution thing as anything. When lakers, as we know them began in the late 1800s they were much shorter vessels being restricted by canal and lock size. Also, since these vessels traditionally had to negotiate very tight harbours and numerous small locks, many times without tug assist, I suspect the navigation was much easier with the wheel house forward. On thee type of vessels you'll notice what appears to be a bow sprit. Its actually a steering pole. Since most of the vessel is behind the wheelhouse its hard to determine the overall position of the vessel from a steering point of view. This pole gives you a reference as tot he direction the overall vessel is pointing when steering it.
When seaway size vessels came about with the opening of the St.Lawrence Seaway this deign continued for a few years more in construction. Many old canalers were lengthened to Seaway Size (730') after the opening of the Seaway. From the mid sixties on vessels were constructed in the traditional pilot house aft configuration. Additionally, except for a few thousand footers on the upper lakes, new construction was also design for salt use.
There aren't many traditional lakers left running anymore, most that run on the lakes are salt water compatible.
I'm sure you've all seen the video on YouTube of the ship loosing its pilot house while going under a bridge. That happened not for south f me in the Welland Canal. The ship was one of Paterson Shippings vessels later built in the bridge aft configuration. That vessel was scrapped by the way.