I feel that cast iron pans are overrated. Stainless steel is easier to clean, lets you build fond, lets you cook acidic pan sauces, and are lighter so you can be more aggressive about pan flipping. The only advantage cast iron has is heat retention and there are few cases where that's useful (like deep frying for example, or baking bread). Iron is actually a relatively poor conductor of heat also and a good tri-ply pan will heat up faster.
Cast iron dutch ovens are another story because you will frequently use them in ovens where the heat retention properties are useful.
The thing about cast iron pans is they're dirt cheap, so it's hard to overrate them.
I guess I agree with you: if you have a high-quality stainless skillet, you don't need the cast-iron pan. Things we do in cast-iron that we don't do in the All Clad pan: make cornbread, sear steaks, grill vegetables outdoors.
I find my cast iron to be a pain, and after trying hard to use it well for years. Slow to heat, slow to recover, touchy to season, and heavy as all hell. I've gone back to either stainless or nonstick, depending.
It's kind of like driving an old F350 as a daily driver. Sometimes its just what you need, most of the time it's a heavy, ponderous maintenance nightmare.
Cast iron dutch ovens are another story because you will frequently use them in ovens where the heat retention properties are useful.