I suspect there's a Parkinson's Law like effect at play. Phones increase battery capacity to meet demands of software which expand to fill available battery life. If a phone is going to have a smaller battery, which is a necessity for a SFF device, it can't be expected to perform the same tasks at the same speed as a full-size phone. But I haven't heard of any OS adapting in such a way. Power management is optimized for the average which is larger than the mini. And not only the OS but the user has to adapt to expect a more frugal experience with a small phone. I don't see that attitude with a lot of people. Nor do I believe advertisers would be happy with a platform that has "use fewer apps" has a selling point.