Most people in the US have unlimited text plans. Either they are built into their monthly bill (Sprint unlimited everything $80 a month) or subscribers pay an additional fee on top their voice/data bill for unlimited SMS.
True, it's a 10 euro addon here for 1000 "unlimited" messages, dropping now however because data usage has grown massively, while the texting cash cow dropped (Whatsapp and BBM).
It's still a bad solution for the problem as a whole.
In the US unlimited messaging typically means just that. And thankfully so, because about a year ago my teenage brother was on my plan and managed to send/receive 16,000 texts in a single month.
16,000 is a large number, but it's not all that surprising. I find myself having multiple conversations at once via text often times, and will spurt out batches of around 100 texts at a time within the course of 5 minutes or so. Teenagers with a social life far more developed than my own will without a doubt hit those numbers multiple times a day.
I think a lot of this is because of the change in mindset of texting. Early on, it used to be a way to convey precise pieces of information. Now it's conversational. People send texts with "um" as the entire message.
Why go through iMessage when you want a direct connection? I think it's just a matter of Apple getting it right and figuring out how to ensure a good experience, yet allowing 3rd party apps to use Siri.
Because using messages you already have access to a lot Siri's understanding. 3rd party access could be very problematic if you consider that Siri would have to understand also several way to say the same things, otherwise it would become just simple keyword recognition.
