Pricing aside, thunderbolt cables are usually thicker and more rigid. Sometimes you need a thin and flexible cable, cheap USB-C cable is a better choice.
And truly lightweight cables, for slow overnight charging (or for charging of small batteries, e.g. smartwatch scale) have all but disappeared with the shift from A/micro-B to C/C. It's awesome that we have near-universal connector for that wide a range of use cases, but that requires some learning about cable classes beyond the old "does the connector fit?" and that learning process is not over yet. And by learning I don't just mean us memorizing classes, but also an effective narrowing of classes, e.g. no more almost but not quite TB4 compliant ones.
Though poor cables do drop the voltage a bit I feel that the proper approach would be to to just use a weak charger. They are "all" USB-A and there are no lack of USB-A -> C cables.
USB4 is required to support Thunderbolt, and USB4 cables are similar to Thunderbolt in their price and thickness, so this problem already exists, just with shittier naming conventions.
Basically for any cheap use cases, you just have to buy a random "USB-C" cable with unknown capabilities, while for specific data use cases you have to buy a "USB-C" cable that also supports a specific data rate, either USB 3.1, USB 3.2, USB4 v1.0, USB4 v2.0, or Thunderbolt 3/4/5 (and most cables will support multiple of these, for example USB 3.2 Gen2x2 is the same speed as USB4 v1.0 and TB3).
I hope I don't come off sounding like a twit, but does fast charging really matter all that much to people? I've had a few fast charge cables before, and although it's fine to have my cellphone fully charged in say, 20 minutes, it doesn't really mean anything to me, given that it will be left plugged in over night regardless.
Perhaps it's more useful to people who are constantly traveling, but for someone who isn't, I guess I just don't see a point in it. Would I turn it down? No. Would I pay more for it? If it's greater than 2$ more, no. Slow charge is "good enough" in my eyes.
I really value fast charging. Normally I turn it off because I do charge my phone at night. But sometimes I really need the boost and it's great that it can do so if needed. Especially because i normally limit my phone to 80%.
I don't use it a lot, probably once a month on average. But the times I do it's invaluable.
It's very important to me. I keep forgetting to plug it in at night and then I can just charge it for 30 minutes before I leave the house and can get a couple of hours usage into it, which is normally enough.
I was frustrated all day because I couldn't find my fast charging cable and just couldn't leave the phone plugged for more than 15-20 minutes at a time due to various activities, which also required a lot of battery charge (photo/video shooting), so I was dancing around the charger all day...
I never charge my phone overnight. My charger is on my desk. I'll typically do a slow charge, but I'll do a fast charge in some circumstances (e.g. when I'm going somewhere soon but my battery is low).