One of the reasons I hate BMW , the sporty car maker , ultimate driving machine factory .. that don’t make a proper sports car let alone a super car, and god forbid a hyper car. Laying all that talent of their superb engineers to waste.
Yes, even us BMW customers would like to see a supercar (what's a sports car these days?) but if it comes to the detriment of normal production models due to things such as budget-shifting, take-from-here-to-give-to-there, reduction of the number of accessible performance models etc. then there's no case for one.
You alluded to it yourself: the rich are spoilt for choice. There's plenty to choose from exotic brands like Ferrari, Lambo, Porsche, Maserati, McLaren. Heck, in the US - a staple market for performance cars in the bracket just below the exotics - you've got compelling and competitive machinery in the form of cars like the C8 Corvette and other American muscle.
Add indirect competition in from performance SUVs and hyper electric cars and the window of opportunity for a BMW supercar narrows further and with it the business case. This really is obvious stuff that even you secretly get but won't acknowledge here.
Instead what we still get - thankfully - from BMW is a range of cars that, even in cooking guise - are well-built and enjoyable to drive for a much larger piece of the market. That BMW makes - and focuses on - cars like the M2, M3 (including the super cool Touring now), M4 and M5 keeps them as the people's champion of relatively affordable performance cars. CS and CSL models only serve to strengthen this position.
They make money elsewhere. It’s not like they would go into bankruptcy. Overall such cars probably raise profitability but in a way you can’t put in the spreadsheets.
I agree, an S-Class coupé is something that would not only garner enough buyers to be profitable (it would be, after all, based on the S-Class) but would do more for Mercedes image, with more of its patrons, than something like an AMG ONE which seems to be a failure in all aspects other than the sheer will to bring it to market.
An S-Class coupé speaks to the core values of Mercedes Benz - that illustrious century and a bit history you mention - of making well-built luxury motor cars far more than does some hypercar that's so complicated it needs two technicians to accompany it to a race track.
And for those saying "yeah typical BMW excuser being defensive for no supercar" let me say this: if I was to go downstairs to drive home in a C-Class instead of a 3er, I can tell you without any doubt: there being an AMG ONE has no bearing whatsoever on making that C-Class a better car.