They're a token option for allowing the CPU to grind for your paid-for content, instead of you yourself having to do it.
Needless to say, the bots are garbage and have been proven already to be entirely unable to beat the game's more ridiculous battles (which serve as content plateaus that stop content acquisition by players); thereby, incentivising further investment into a money-for-good transaction that consumers completed at point-of-sale.
NB: MK11 is not a "games as a service" or subscription based game, nor is it free-to-play. Yet, it is replete with micro-tranny scams and content gating that would make most f2p MMO's look like 90's era stand-alone games!
The system was present in Injustice 2 and, from what little I did dabble with it, the CPU at least did acquire some content. However, those were the prototype content ransoming models NRS-Warner were testing out; whereas, MK11 is the "version 1.0" of their erstwhile fighting game franchise, now evolved to a micro-tranny harlots harem.