They eliminated the move some years ago, primarily due to insufficient sleeper traffic from Boston and a shortage of Viewliner sleeping cars.
The shortage of sleeping cars was indeed part of the problem, but lack of sales of the rooms in the sleepers was not an issue. That sleeping car was typically at least 3/4ths sold by the time it reached Albany, if not sold out.
Beyond the shortage problem, part of the reason was Amtrak's desire to rotate all Viewliner sleepers during the winter onto a warm southern route after a run on one of the colder northern routes to help prevent freeze damage. Sending a sleeper to Boston did not accomplish that goal. The second reason is that with the demise of the sleeper on the Twilight Shorliner/Federal, eliminating the sleeper on the Boston section eliminated the need to keep parts and Viewliner trained workers in Boston.
The third and final reason, was the continual failure of the yard crews in Albany to accomplish combining/seperating the Boston section from the NY section in a timely manner. It was simply taking far too long to combine/seperate the two trains, which consistantly caused delays to the Lake Shore.