This is key. When a rivet gets loose you can feel it, you have some warning. Then you can either drill it out and replace it or give it a bonk with a hammer to tighten it up.

Spot welds fail without warning and of course under load, which is when the pan is full. Also, when they do fail it is not usually possible to make a repair. Spot welding machines are very expensive and difficult to set up. You can drill out the area and put in a rivet but that is often tricky given the remains of the failure.

No spot welded handles in my kitchen.