To me this argument makes no sense. Apple should never introduce any new features or services to their ecosystem because it might increase “social pressure” to get an iPhone?
Meanwhile, we take it for granted that there is a protocol for audio calls and text messages but not for video calls. I would like to more easily video call people with iPhones, and doing so would be technically possible but I can't because Apple benefits from the network effect. If I were to get an iPhone it would not be because Apple did a better job at creating a video call feature, it will be because people I know have iPhones and I want to call them. This seems like it gives incumbents in the space a large advantage because they can compete on having a user base and not on quality.
Ironically, Apple itself developed such a protocol for events and RSVPs (ICS), at a time when they didn't have market dominance. This caught on and it is great. I can make a calendar event in Google Calendar, Outlook, or Apple Calendar and invite anyone from any of those platforms. They can RSVP and I can track their RSVPs and they can also create events in their systems and invite me. This is the kind of thing I like to encourage where possible.
Technically vCal/iCal/ICS (whichever name you prefer) doesn't actually support RSVPs. It isn't in the standards documents. In ancient Microsoft nomenclature that pseudo-standard (de facto standard) for RSVPs is the "Schedule+ protocol" named after an ancient dead predecessor to Outlook's Calendar which originated it. I don't know what Google or Apple call it, and it is such a weird dance of (usually) auto-deleted email messages, so certainly has room for improvement as a protocol.
It would be neat to encourage a new "modern" standard there. Seems like something more web-based (JSON REST API?) than email-based might be a more "natural" API today. (Maybe Apple Invite can help lead the way, I don't know if that's on their TODO list.)
Certainly some implementations are pretty poor, but in theory this is all standardised.
The US Department of Justice is currently suing Apple for violating those antitrust laws [1]
[1] https://www.theverge.com/24107581/doj-v-apple-antitrust-mono...