Technological advances and AVR chips
Just recently I stopped to think about AVR's. There's something astounding about a chip that costs a couple of pounds and yet has a fully implemented processor, memory, flash, serial IO, ADC and reprogrammable ROM. Just think that's basically almost as powerful as an old 8 bit computer from the 80's in an 8 pin DIP package. To put that in some perspective, the old 8 bits had countless support chips and their power requirements would be well in excess of any of the ATTINY range of Atmel's chips.