They hope you will break the speed limit so they can make money, that's why.
In the UK, for example, about GBP 80 million in speeding fines are issued each year. The annual police budget is GBP 12.5 billion though, so fines are a tiny 0.64% of that, hardly significant. Having said that, it looks like the road policing budget for 2018-19 is down by a large amount, from the GBP 200 million in 2016, to about GBP 90 million, so the fines would seem to cover most of that... Not sure what to make of that, now?
There are also groups of car enthusiasts and people that legally race cars and modify cars to squeeze every ounce of performance.
This whole page is filled with "Doesn't apply to me, so go for it", which seems like a really bad rationale to apply to hundreds of millions of people, potentially.
It's from 2007: https://www.autoblog.com/2007/12/22/nissan-gt-r-recognizes-t...
Surely those who have track days can disable the limit or buy a car without it, while the vast majority of "casual speeders" won't be affected by it.
Even 112 is quite high compared to the speed limit in most of the world. 100 would be right, outside Germany.
on the other hand, it looks like they are just limiting the speed based on the rating of the stock tires. as long as there's a straightforward (and legal) way to increase/remove the limit when you upgrade the tires, I'm not sure I have a huge problem with it.