It is because the modern ones really sound poor.
After watching numerous reviews, even Chris Harris driving stuff like 488 GTB, 488 Pista and after me personally driving the 488 GTB and Portofino I can tell you now that irrelevant of what the manufacturer says, irrelevant of what the reviewers say these cars do not sound good, they sound not a patch on the 458 or the other atmospheric engines and they state turbo lag free, that is also another lie, I drove a Portofino over two days in all conditions and though its an excellent car, there is turbo lag, but I will agree it is absolutely minimal and the engine does rev out nicely, but of course its always more about mid-range with a turbo motor no matter how hard the manufacturer tries to make the power delivery replicate NA.
To put it simply a 458 with stock exhaust sounds much better, much louder than a 488 Pista or 488 GTB and even louder than a Portofino to you the driver even with roof down.
I like a proper sounding engine, screaming flat plane Ferrari V8, screaming V10 or a traditional throb throb throb American V8.
I drove an M2 Competition yesterday and I'd go as far as saying BMW have truly nailed it as far as turbo motors go, yes its got lag but its got a serious kick around 5000rpm that holds nicely until 7000rpm and believe it or not from the outside its still got that lovely straight 6 noise too, the only disappointment inside the cabin it was so quiet, no classic NA induction noise or roar which is a shame and I was driving a stripped out M2 Competition on track, what I will say is what a car, the handling in MDM mode was ace, you can get some serious slip angle and drift the thing with the safety of the computers making you feel hero, but even then it was very progressive and easy to modulate which sometimes turbo motors can struggle.
For me the M2 Competition is the best BMW since the E46 M3 CSL, seriously what an awesome little yet big car.