In lots of countries, SMS have basically gone the way of the dodo and are chiefly used for automated messages. I haven't received a single SMS from an actual human being in several years, since everyone just uses chat apps such as Whatsapp, Telegram or Facebook Messenger.

In those countries where Apple didn't have a > 50% market share in the early '10s, people simply couldn't use iMessage. For instance, this is a summary of how things went in Italy. I think something along these line could have happened in most other countries where prepaid traffic was the norm though:

1. In Italy, basically the entirety of mobile plans were and still are prepaid, which meant you charged your account with money which you then used to pay for your traffic. Most people also had plans you could easily change, which gave you stuff such as SMS and phone calls minutes for a fixed fee, and you paid for them using prepaid credit. More "serious" contracts were heavily taxed, and thus only make sense for corporate phones or if you have a VAT account to deduct some of the taxes (and even them they were not the cheapest option).

2. No prepaid plan included unlimited SMS until around 2015, when they had already become largely irrelevant to most people. Before then, you generally got a very limited amount of SMS per month or day, and those were often tied to numbers belonging to the same carrier.

This meant that most people in a certain area were basically forced to stick with a certain MVO for most of the '00s. For instance, a very popular 2007 Vodafone prepaid plan in Italy costed €6 per month, and included 100 SMS a day towards all Vodafone numbers (99 actually, you had to pay the first one). Having the "wrong" carrier in that time period meant that people had to pay a lot of extra credit to have a proper conversation with you - this was often a deal breaker for romantic relationships among teenagers, or led to people not contacting you at all. A very interesting time indeed.

3. MMS were basically never included in any plan ever, and when they did, they had the same limitations as SMS. Often, if your plan followed the "pay the first message, get 99 free" clause this was also true for MMS, meaning you had to pay for the first SMS AND the first MMS. If People were so wary of them that they actually deleted the MMS APN from their phones to avoid sending one of them by mistake - if you wanted to send a photo to someone you simply waited until you got home, in order to use MSN Messenger or email. The only usage of MMS I remember of in the '00s was sexting.

3. When iPhones and Android came out in the late '00s, data packs suddenly became a necessity to most early adopters. The iPhone heavily pushed its Internet capabilities a lot, and you often had just spent a hefty sum (remember: prepaid meant you had to pay the whole phone cost upfront) so you wanted to squeeze value out of it. Carriers at the time came out with the idea of selling extra prepaid packs with a limited amount of data (i.e. 50 MB a day, or 500 MB a month), which was not an awful lot but it was enough for maps and some light browsing.

4. I actually bought an iPhone 3G back in 2008, and it was truly amazing for its time. I paid around €550 for it, which was quite a lot for a teenager - I had to sink a lot of the money I had earned from my summer job in order to buy that. Most people around me were very against the idea of spending so much money on a phone - after all they could get by by simply buying a random Nokia 6610i or whatever for €100 and pay your 10 euros a month in prepaid credit and do whatever you needed to do. The fact that carriers in countries like the USA basically forced you into 2 year plans meant that you often got iPhones for cheap, which helped get a foothold in the market.

5. When people started to actually switch to smartphones around ~2011, most people picked up shitty €200 Android phones which utterly sucked, and the higher end saw a lot of fierce competition between the iPhone, Samsung Galaxy and the likes. Still, you could expect at most 1/5 of your contacts to have an iPhone, and still people were locked in those carrier walled gardens when sending SMS. If they had an iPhone you could send them iMessages, but that was not the case. The fact iMessage was integrated in the SMS app didn't help either: people back then had to actually _count_ how many SMS they had sent a day to stay under their daily caps, and mixing in special messages you didn't have to pay was actually pretty confusing. I think most people in Italy today still don't really know what iMessage is actually.

6. Data is carrier agnostic - as soon as true chat apps with push notifications such as WhatsApp and FB Messenger came out, people started using them as a loophole to avoid paying for MMS and SMS. Group chats, which were really not feasible before (remember: SMS caps), suddenly became popular. Feeling left out, most people left feature phones in order to use chat apps, causing SMS to quickly disappear in less than a year. As an example, I went from sending 100 SMS a day in 2012 to 20 a YEAR in 2013.