Chase negotiated a flat rate to use the Visa network (not a percentage cost), so any work to support MC beyond what is required by the co-branded partner is not of interest.
https://creditcards.chase.com/mastercard-credit-cards
I remember Chase Freedom had a prominent MC option, did all of those cardholders get converted? (Yes, in 2014. Hilariously, the conversion notes referred also to Blink, the contactless tech that was removed from all Chase cards. So sad.)
At its current rate, I expect Chase Pay to not survive. A few restaurant offers and the fuel offer that are too difficult to use (too much friction) are not going to work. Then, they further dropped their version of Amex Offers, so really not useful.
Maybe there is some hope for a compelling situation for me to consider using Chase Pay again, but I see more benefits this year to use Chase via Samsung Pay than Chase directly itself (so sad again).