Lots and lots of reasons.

I’m basing this on your comparison of normal cars to currently existing exotics.

Predominantly - the vast majority of people don’t want an exotic car. They want to go from home to work and the store, maybe a drive for a leisure trip. They’re boring. They want to get their stuff and people in and out of the car easily and conveniently.

Exotics do not do this well. There’s minimal trunk space and fit two people, often “snugly.” They require some contortions to get into and out of. Now think of how out of shape many people are and see if they fit into a highly contoured and snug race seat and can crawl in behind a scissor- or butterfly-style door with a very low roof.

Engineering-wise it’s a big cost issue, both for the manufacturer and customer. Those compact, low, aerodynamic bodies on exotic cars take a lot of work to pack all the mechanicals in along with having to design a body that is crash-worthy for each new exotic style. On top of that, they’re often mid-engine, which means a lot of specialty parts like transaxles, and wildly different handling characteristics than the average consumer is used to when you shift weight to the back of the vehicle.

Manufacturers are sticking with the “boring” designs because they’re based on existing engineering that is safe, requires minimal cost to make the new iteration, aerodynamic, fuel efficient, and has proven to be sellable to consumers. Profit is king. They’re not going to take chances on crazy styles that may not sell because again, people are boring.

I know people are going to chime in about mundane cars in production today that have some of the features I mentioned and treat them as an exception that invalidates the opinions I’ve offered, but the point is that if they were economical and profitable designs in an exotic body they would be more widespread. “You could just take “x” engine and transmission and build a “y” around it” argument.

I would suggest maintenance is a cost problem, too…some exotics literally require the car be split - the entire rear of the car containing the engine and transaxle removed from the rest of the car because of the compact engineering and inaccessibility to some wear parts. However if Toyota made a low-buck supercar looking commuter car I’d hope the maintenance would be cheaper and easier.

So there you have it. Cost of design, engineering, and maintenance. Boring consumers, convenience, and safety. Affordability and profit. That’s why we don’t have exotics everywhere. The market has determined that the few Halo cars we see like the Supra or C8 Corvette, or even the Mustang, is all the market will bear.