There's only one reason why.
As history has shown, BMW has launched a generation Mini about every six years. The current third-generation Mini hatch has been on the market since 2014, so you'd think it'd be correct to assume a successor should be coming just about any time. Thing is, it's wrong to assume in this business. Things change and automakers have to adjust. According to Reuters, BMW has put the next-generation Mini on hold as part of a cost-cutting effort due to uncertainty over Britain's trade relations with the European Union following Brexit. Until these trade issues have been fully worked out, long-term investment decisions are extremely difficult to make.
"The lifespan of this platform has been extended," BMW spokesman Maximilian Schoeberl said. "For costs reasons and because of Brexit." Unlike BMWs, which are mostly built in Germany and the US, Mini production takes place in Cowley, Oxfordshire, England.
Is it possible for BMW to close that facility down and move production elsewhere, say mainland Europe? Yes, but doing so can't be done overnight and, not to mention, expensive. Mini sales have not been extraordinary over the past few years, meaning an investment as large as building a new factory outside of the UK may not be worth it. BMW purchased the iconic Mini brand from Rover Group in 1994 and very successfully rehabilitated it beginning with the first-gen completely redesigned Mini in 2000.
Since then, there's been the Mini convertible, Mini Countryman, Mini Clubman, and, more recently, the Mini Electric all-electric hatchback. Mini aims to focus more heavily on battery-electrics going forward.
Fortunately, parent company BMW has the necessary technology already developed or in the works, thus cutting some future costs. The good news is that BMW refuses to give up on Mini. In China, for example, BMW has teamed up with Great Wall Motors to build a new Mini factory solely for battery-powered Minis. For now, those vehicles will be for China only.