Why did blackberry services require separate mobile Internet settings (APN blackberry.net, for example), and therefore special support from the mobile operator, while smartphones from other manufacturers (Android, iOS) were satisfied with the usual settings?
It seems to me that the point there was instant message delivery, and on the normal mobile Internet under NAT incoming connections are closed, and it is expensive to keep the session behind the NAT, polling the server is not as fast. Therefore, on a separate APN could be a special server that has access to the internal IP-addresses of the phones directly, without all the NAT and the possibility of incoming connections. A message came in, the server sends it directly to the phone's IP. And mobile IPv6 was not yet widespread back then.
And Android and iOS came later, when the networks and capabilities of mobile devices were more developed, and the requirement for prompt delivery was not so obvious (even now often mobile notifications come with a delay), and therefore a normal session from behind NATa was enough, the more it is easier and special support from the operator is not needed for this.
How did it really work?