In one of the most overused tropes on the show, it’s them trying to hide the fact that they are living together from their respective parents. I mean, they were in their late 20’s and maybe even early 30’s! Who cares what the parents would think!

The second episode it made sense when Chrissy's mom came. Eleanor moved out and her parents did not know Jack moved in. It got really dumb in season 5 when Janet wrote a letter to her parents that she got married and Jack pretended to be her husband.
But its crazier in the last season when the quiz in the magazine makes Jack think the girls have a crush on him. The gay stuff with Jack got really stale too.

That was a dumb one! Ironically, Janet’s parents weren’t at her real wedding, lol.