No single app can dominate the market because National Payments Corporation of India has decided to impose a cap on transactions that a single payment application can process.
https://www.bloombergquint.com/business/npci-imposes-cap-on-...
https://www.bloombergquint.com/business/npci-imposes-cap-on-...
If you’ve already reached your 30% cap, what incentive do you have to improve your service?
By having to compete with other services who are trying to get your share?
Government may also remove wallets (which aren't part of UPI) completely in future through regulation.