Ads are a complicated thing. American TV is designed with ads in mind. So it has natural breaks for them. If you are going to insert ads into American TV content, then those breaks are the natural and obvious place. Putting them anywhere else interferes with the pacing of the show.
No ads is great. Upfront ads are not so bad. Ads in random inappropriate places in the show SUCK. Ads in the engineered commercial pauses are not ideal but they're better than being at random.
The ads themselves vary in quality, relevance, and annoyingness.
The devil's in the details. You can distort the questions and the numbers to generate any result you want.