Sure, and mainstream texting predates the iPhone by several years. And the iPhone wasn't an instant hit over here, either. Too expensive, both the hardware and the data plans. Hell, I already had a full time job by then and even being a techhead I waited several generations and only got an iPod Touch because getting the GSM version seemed like a waste of a LOT of money just to get access to the App Store.

But still, MSN's dominance predates texting and it just kept that role while texting was a separate way to catch up with people on the go. And yeah, it was expensive, or at least paid piecemeal, so people went as far as using their phones as beepers, giving each other little deliberately missed calls to point them towards other messaging apps or social media. Because social media also happened, and it also predates smartphones, and it kinda took over for MSN Messenger. By the time Android phones got big over here, let alone data plans or SMS became the norm, those became the default.

So yeah, the economics of it all drove the adoption, along with companies being more regional (no ICQ or AOL over here, either), but it's more of a series of mismatches in the timeline, rather than a direct line from SMS pricing to Whatsapp. There are multiple different tangents along the way, and they're different in different places.