Sure there is. If you try to "text" someone (as in SMS) and the Messages app (which is the ONLY way you can send SMS on iOS) detects your number as registered to iMessage, it will send an iMessage by default.
So even though your number didn't change, and everyone is still using the "Messages" app to talk to you, it inexplicably doesn't work anymore for group chats, and your regular private message colors have mysteriously turned green.
There are plenty of SMS-API-provider-backed "texting apps" on iOS. There are also softphone apps that provide SMS service.
I think you specifically mean "the only way you can send SMS messages from the DID number that your carrier maps to your phone's MMC IMEI registration.
Except for the vendor lock-in, which makes this a problem to begin with. Other services work on a majority of devices.
Which is a legitimate complaint especially since Apple had said they would be opening it up (or was that FaceTime...I'm not sure).
But that's a wholly different complaint from the fact that Apple, like nearly every other messaging service, does not allow you to export groups to other services.
Apple consciously doesn't make the APIs for iMessage available.
WhatsApp doesn't provide an API so I could use it on my existing laptop over WiFi for free (the WhatsApp web requires it to be setup on a phone first).
But the phone doesn't have to be bought from Facebook, whereas with iMessage you have to pay Apple for a phone.
>maintain a phone line to use WhatsApp.
I wonder what the reason for this is. Maybe to reduce spam? Data collection?
maintaining a phone line doesn't cost hundreds of dollars a year
WhatsApp works reliably on a staggeringly broad list of devices. You can get a supported phone for, like, $20 and stick a $5-per-month prepaid SIM in it (many of these plans in low-income countries specifically come with WhatsApp allowances) and be connected.
This is like arguing that free Wi-Fi isn't "free" because some people only use ethernet. If you don't already own a compatible device, you aren't their customer anyway.
Sure it is! You can't continue a group conversation from WhatsApp -- or any other messenger, really -- on another messenger service without manually recreating the group. There is literally nothing which makes iMessage unique in this regard.