> increasing cache locality is orthogonal to how much RAM an app is using. It just lets the CPU get cache hits more often, so it only relates to throughout.

Cache misses mean CPU stalls, which mean wasted CPU (i.e. the CPU accomplises less than it could have in some amount of time).

> In the case of Electron apps, they use a lot of RAM and that's not to spare the CPU

The question isn't why apps use a lot of RAM, but what the effects of reducing it are. Redcuing memory consumption by a little can be cheap, but if you want to do it by a lot, development and maintenance costs rise and/or CPU costs rise, and both are more expensive than RAM, even at inflated prices.

To get a sense for why you use more CPU when you want to reduce your RAM consumption by a lot, using much less RAM while allowing the program to use the same data means that you're reusing the same memory more frequently, and that takes computational work.

But I agree that on consumer devices you tend to see software that uses a significant portion of RAM and a tiny portion of CPU and that's not a good balance, just as the opposite isn't. The reason is that CPU and RAM are related, and your machine is "spent" when one of them runs out. If a program consumes a lot of CPU, few other programs can run on the machine no matter how much free RAM it has, and if a program consumes a lot of RAM, few other programs can run no matter how much free CPU you have. So programs need to aim for some reasonable balance of the RAM and CPU they're using. Some are inefficient by using too little RAM (compared to the CPU they're using), and some are inefficient by using too little CPU (compared to the RAM they're using).