Why does Boeing use a trim wheel in the 737 and not their other products?
Trim pitch "wheels" as you describe date back to the time when turning that wheel actually pulled on steel cables that were connected to the hinge mechanism for the control surface itself. This mechanical/manual system was a simple and robust method of manually trimming the aircraft and was very widely used before electronic/fly-by-wire control systems were invented. 

Since the 737 is the oldest basic design platform in the Boeing product line, its original design dates back to a time when trim wheels were mechanical and pilots were transitioning out of still older planes into Boeing's new offerings- and those pilots expected manual trim wheels. 

It is likely that trim wheels in newer planes are a "legacy" feature, allowing pilots familiar with an older revision of the cockpit layout to transition to another newer plane in the design series.