Despite reports of Talking Smack being cancelled due to low viewership, according to Justin Barrasso of Sports Illustrated, the reason for the weekly format coming to an end was due to Vince McMahon. The unscripted style of the show played a part as Vince was not pleased with the show and felt it wasn't best for the company's interests.
While still very connected to his TV shows, Vince has been reportedly less physically present at TVs, as of late. He was present last week and made the decision to cut the weekly format, and, per McMahon, eventually end it altogether.
"We continuously review WWE Network's programming line-up based on a variety of factors, including viewership and subscriber research. Talking Smack and Raw Talk will air following pay-per-view events, and Tuesday will continue to feature 205 Live."
Source: Sports Illustrated