Not sure why. Maybe because the quality isn't there anymore. Maybe they resorted to tried and true ratings gimmicks such as episodes in exotic locales, weddings, characters leaving and new ones coming in, etc. Here is my list of current shows I watched loyally but I just gave up on. Do you have a list and why?

2 BROKE GIRLS
Bones
New Girl
Hawaii Five-0
Elementary
Madam Secretary
Big Brother
Survivor
The Amazing Race
Undercover Boss
Law & Order, SVU
The Voice
Modern Family

1. Quality (Far and away #1)
2. Lack of interest in the subject matter or cast

Most of your list exemplifies why I lose interest: repetition. Sitcoms are easiest to tire of, in my experience. Probably followed by procedurals.

L&O SVU is another good example of too much repetitiveness. The show ran its gamut ages ago, and ought to be retired; it started wearing thin when too many of the stories became about one of the detectives, or other regulars (usually Olivia) being the main point of the episode instead of focusing on the reality-based crimes, with the detectives solving them.

Modern Family became the Ed O'Neill Show sometime back, and is these days more about his mugging his way through each installment than anything else.

Elementary was based on a gimmick that became tired after just a few episodes in.

Bones: how long can you maintain interest in a show that seems to be chiefly based on showing us lingering closeups of former human beings who've become maggot-infested puddles?

50 Is The New Cutoff Age.