Everything where high interoperability is more beneficial for consumers than proprietary solutions by individual companies. As a rule of thumb, everything where standardization brings more benefits to consumers than innovation.

Note that as consumer, I can't vote with my money for standardization. I can only vote for one of the proprietary solutions. So if 70% of consumers stick to one option, and 30% stick to the other option (because of other product features), standardization will never happen through market forces, even if 100% of the consumers would want it.

It gets even worse when more than 2 options are on the market, and vendors gain an advantage by locking customers in to their proprietary option.