One would think, but no. I have bought brand new pans that were slightly warped on the bottom. On a ceramic top stove, the pans have to be absolutly flat to get even heating.
Laying a heavy ruler across the bottom will help you see if the pan is flat or not.
Once, I bought a new stock pot and could not get a rolling boil because of the bottom not being flat.
And, as expected, more expensive heavy brands do tend to be flat while cheap pots and pans tend not to be.

it's not just warping, some pans are made with indentations and ridges. (Most stove-top grill pans are REALLY ridged). The advice that came with our stove said take a metal straight edge (ruler) and place the one edge across the outside bottom... if you see daylight under the edge of the ruler, it's will not make full contact.

Plenty of thin pots and pans are not flat on the bottom, and if you put them on a flat cooking surface you'll find that they wobble. And the thinner they are, the more likely they are to warp and dent.

I got some Revereware and Farberware 30+ years ago as wedding gifts. I used them for 30 years on my cheap electric ranges with not much problem. When I remodeled my kitchen a few years ago, I found that the Revereware pots fell off my new gas cooktop grates. The Farberware did better, it has a heavier bottom, but I ended up having to get a lot of new pots and pans with heavy, flat bottoms.

If you are especially unlucky you may even find yourself with a pot that is perfectly flat when cold and goes wobble when heated. When you read about some of the exotic manufacturing methods used, it is really amazing that a flat bottom pot is even possible.