Also because no one else is offering a car that will compare with the 1er coupe or convertible.
I think the car will stand on its own, although I agree that the inflation of the 3-series in both price and luxury makes a lot of room for the 1er.
No other luxury compact out there will have the following combination of credentials:
semi-affordable
4-seats
6cyl engine
rwd
available ragtop
sports car handling
coupe layout (i.e. trunk, not hatch)
Nothing from Audi, Merc, VW, Acura, Lexus etc. will have the combination of the above characteristics. It is keying in to a somewhat subtle gap in the market in the same way the Miata did for sports cars in 1999. At the time there was no credible rwd roadster at an affordable price point, and, given the success of the Miata, this represented a significant gap in the market.
Sure there are credible offerings available and to come for those who want a high-end sport compact, but the 1er coupe/convertible will be a on-of-a-kind model range, as things stand... And I think it will key in to a balance of price
erformance:appearance
racticality that will really appeal to many "real world" car enthusiasts... I really think it's filling a gap in a similar way to the Miata...