It's a billion pound a year market, people generally buy a hot hatch to tune it. If their cars are sh!t and untunable then they won't sell. Look at the latest Yaris SR, how many of them have you seen on the road? Great price, great spec', but absolutely no following or potential in the tuning circles. Then look at something like a Fabia VRS. Not particularly high spec', not particularly quick, but there's loads of them about because the price is keen and they're easy/cheap to upgrade.
There will be a degree of consumer opinion involved in technical decisions. Otherwise, who are they making the car for and how do they know if it will sell? Of course they gauge owners opinions and the easiest (and free more importantly) way to do it is via forums and such like. Hence why RS came out last week defending the new gearbox in a press release, if they don't keep an eye on things how do they know it needs defending? Social media is a very powerful business tool these days...