Vince McMahon is rarely seen on WWE TV these days and while he returned a couple of years ago to try and get Roman Reigns over, his Mr. McMahon persona is pretty much non-existent these days. Instead, he concentrates on working behind the scenes, appearing only sporadically for major events like the Greatest Royal Rumble or for announcements like the upcoming Evolution PPV.
According to Dave Meltzer and Bryan Alvarez, the main reason Vince no longer appears on TV these days is because he's looking much older and the WWE Chairman would rather not be seen.
You can understand why he feels that way as while he may not look his age, he still isn't in his prime and WWE Superstars beating up an old man won't have quite the same impact as when he used to clash with Stone Cold Steve Austin. Even behind the scenes, it's said that Triple H and Stephanie McMahon handle broadcasting deals and the like and there is a transition of sorts now going on.