system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why are cordless tools rising in voltage?

I’ve owned cordless tools of various kinds since I was a teenager and they were always marketed by voltage. In the nineties, 9.6 volt was the big thing. Then in the 00s it was twelve volt, and eventually 24. Now it seems like the larger tools are all 40 volt and above, but not all; my chainsaw is 24 volt and cuts down small trees just fine, and my string trimmer is 40 volt and doesn’t seem to be any more powerful than the chainsaw but the battery lasts longer. 

What I don’t understand is why these things seem to be growing in voltage rather than amperage, and in marketing it seems like the voltage is supposed to be a proxy for how powerful it is. I understand the larger tool needs more power but why are the cells wired in serial rather than parallel?
gpt
The higher of voltage you run, the smaller of conductors your need to pass the same amount of power. So 100W of power at 12V is 8.4 amps. But if you jumped it to 24V, it would only be 4.2 amps. And 48V would be 2.1amps. So raising the voltage will let you get the same amount of power out of a tool but not need big copper wiring on the inside.