Apple hasn't been found to have violated anti-competitive practices in courts of law. You have legislators claiming that they're acting in an anti-competitive manner without any court rulings to back it up. Using caps is the way for legislators to get around the fact that Apple has not been found to be in legal violation.
As I've said before, legislators around the globe have never bothered to do an actual comparison of prices, quality, selection and customer satisfaction with apps for iOS versus Android versus Windows versus Mac. That should be an easy way to show lack of competition and it's not being done...because the legislators know it wouldn't provide a favorable comparison relative to their legislation.

EU says Apple’s App Store breaks competition rules after Spotify complaint
Apple has "abused its dominant position" in the distribution of music streaming apps, the European Commission said.
I am pretty sure I can find more.