There is a very real question about whether anything needs to be simpler than a $5 chip
For me, the primary driver is physical size. An eight pin DIP is the perfect size for a handheld gadget.
Regarding costs... I've been getting very good results using the internal 1 / 8 MHz oscillator, running directly from batteries, and not bothering with a pull-up on RESET. For me, "bare bones" is just the processor making the cost difference $15 versus $2. For the three gadgets I've built that's $45 versus $6. Enough of a difference that I'm certainly going to continue using tiny processors! (when appropriate)