Oh, I know. There's so much additional runtime for adding virtually nothing to the actual plot.
It's a decent element though in a very cynical way, in that what you've essentially got in Joi is an app fostering expensive purchases. There are analytics firms that use your app behaviour and other metric data on your phone to alter app behaviour, everything from the tenor of notifications to the prices that you pay for in-app purchases. Joi, despite obviously being written as the heart of the film, is actually the avatar for the soullessness of the age of digital companionship. It's a powerful AI that encourages emotional co-dependence through the manipulation of innate pscyhosexual behaviour in men and then essentially uses that most potent reason-robbing cocktail of testosterone, dopamine, norepinephrine and oxytocin to extort money from you. How, you may ask? What's the very first interaction between K and Joi? He presents it with a surprise: an emanator, which as a mobile holographic emitter capable of housing a complete AI, can't be cheap, just so he can keep his personal drug with him at all times. How convenient, no? It's fairly insidious when you think about it. The payoff for that is when he encounters the massive Joi hologram that calls him by the same name as his 'version'. It is in that moment that he comes to realise that everything that has defined him as a being to that point, the dream and Joi, are nothing but fakery meant to keep him shackled.