I think the free nature of these services is what leads to this fragmentation.
Slack is an outlier because you don't actually need to communicate with everyone in the world on Slack.
But for others, it would be completely unreasonable to ask your acquaintances to pay to install Skype to talk to you. And you probably wouldn't pay for Skype if it didn't interop with whatever other people were paying for.
In a world where switching costs for consumers are so low, interop becomes less important because you can ask your contacts to install an app if it's useful enough.
No. I won't install a privacy invasive app (which they all are) just because you have it, never. SMS or nothing if we don't already use something else we'd rather use.
That is true but quite beside the point. If that was my only worry I'd have much less friction to install random spyw-ehm messaging apps.
(I believe that operators generally have much tighter regulations and laws governing what they could actually do with that, but regardless - besides the point)
There are other privacy concerns with messaging apps: e.g. harvesting of contacts, access to media and photos and camera on your device etc. Perhaps he/she means those.
Sounds likely. I'd say that there's still a decent cost in terms of setting up and maintaining all these different accounts, but I'm sure many users don't see it that way, or don't care.
Slack is an outlier because you don't actually need to communicate with everyone in the world on Slack.
But for others, it would be completely unreasonable to ask your acquaintances to pay to install Skype to talk to you. And you probably wouldn't pay for Skype if it didn't interop with whatever other people were paying for.
In a world where switching costs for consumers are so low, interop becomes less important because you can ask your contacts to install an app if it's useful enough.