The old way is actually the analog style you've mentioned, but that was the very early days of ecigs well before they became mass market, the cottage industry modding scene had no hope of creating sophisticated microcontrollers and the charger wasn't even USB, it was a DC jack & plug. Lavatube was the first time we had that kind of microcontroller regulation & then the DNA15 and DNA20 came out, got cloned by China and that changed the game forever.

The problem with the older way is consumers understand watts alone as a relatively consistent measurement of power much better than they would the relation between voltage, resistance & current draw. They didn't want to learn Ohm 's Law back then and wouldn't want to know about it now. Microcontrollers simplified that massively.

Yeah, it doesn't make much since if you think in terms of how many transistors are needed to implement each of them as the microcontroller probably uses hundreds of thousands more transistors than a 555.

That said, given reasonably recent processes die size for both are probably pretty close (I reckon most of the size of a modern 555 die would be the points to place the wires to the package) and with pretty similar yields (pretty close to 100%)

I wouldn't be surprised if the reason has something to do with economies of scale since a cheap microcontroller can pretty much be used for the same things as a 555 and a whole lot more than that, so it makes sense more of the former are manufactured than of the latter, plus I bet the process generation used in making the microcontroller is probably more recent and hence one where there are more fabs operating. This latter reason would also explain why this more recent 32-bit microcontroller is actually cheaper than older 8-bit ones with less built-in memory and fewer peripherals (such as the ATTiny ones).

It was a good insight into how the lightbulb dimming tech of the 80s/90s worked. Also why the dimmer switches back then were so dangerous with the capacitor likely just a few mm's away from the light switch which might not have been properly wired because UK homes back then didn't run a neutral back from the switch, but daisy-chained the switch and the bulb together and then ran the neutral back from the bulb