I'm sure they do that on purpose to emphasize the imperfections of puppetry... think back to when Tyler Bunch did that Barnone dog, you could see like half his entire arm in those commercials. It's kind of like Danny Antonucci's approach to Ed, Edd n Eddy by emphasizing imperfections of cartoons from the golden age of animation.
And not all commercials that use puppetry do this; back in the early 2000s, there was an Eggo commercial with a dude whose roommate was a lizard puppet: while the puppet itself was kind of crudely made (sloppy, visible seams, the fabric that covered him was plaid, his eyes were crooked), the illusion of the puppet itself was done really well: there were no rods, no strings, plenty of full-bodied shots, so there was probably a lot of chromakey used. Plus, it was funny...
LIZARD: Hey, Hal... are those Eggo waffles?
HAL: (Scoots plate away) Yeah, they are...
LIZARD: Aren't we forgetting something?
(The lizard reaches for the waffles, but Hal moves them away further)
LIZARD: It's always nice to share!
(The lizard reaches around, but Hal grabs his hands, and literally ties his wrists together; then ties his shoe laces together, and flops his legs over his head)
LIZARD: You got some serious issues, pal!
And not all commercials that use puppetry do this; back in the early 2000s, there was an Eggo commercial with a dude whose roommate was a lizard puppet: while the puppet itself was kind of crudely made (sloppy, visible seams, the fabric that covered him was plaid, his eyes were crooked), the illusion of the puppet itself was done really well: there were no rods, no strings, plenty of full-bodied shots, so there was probably a lot of chromakey used. Plus, it was funny...
LIZARD: Hey, Hal... are those Eggo waffles?
HAL: (Scoots plate away) Yeah, they are...
LIZARD: Aren't we forgetting something?
(The lizard reaches for the waffles, but Hal moves them away further)
LIZARD: It's always nice to share!
(The lizard reaches around, but Hal grabs his hands, and literally ties his wrists together; then ties his shoe laces together, and flops his legs over his head)
LIZARD: You got some serious issues, pal!