If people don’t “enjoy” wearing particle masks they are free to breathe smoke and filter the indoor air with their lungs instead. I have worn one for eight hours many times when walking around cities with awful AQI scores and by far the most annoying thing about it is the condensation. You also don’t need “perfect” insulation for there to be a benefit to filtering indoor air, the simple fact that it moves around less means that it will clean up in a way outdoor air can’t. The “air purifiers” you can buy with filters built in are easy to use but at the end of the day they’re nothing more than a fan and a filter with air being forced through it.

And as a final point, you seem to just fall back on the fact that there are shortages as an indication that there’s nothing to be done, and this will soon be “over” anyway. First of all, you don’t know that, and secondly, if you live in an area where this is happening, it will happen again sooner or later. If you have nothing at home to help you filter the air you’re breathing, at least prepare for next time. Disposable particle masks are not a waste of money, they’re cheap and last forever.

Is that true that the smoke will get in after a few hours? Over the last few days, as soon as I step outside, I can smell the smoke out there really bad. I thought for sure that if it was smokey in the house, my nose would be used to the smell. I mean, I can see some particles getting into the house, but it has to be far better indoors doesn't it?

Certainly yes, it's better indoors. However long it'll take will depend on how good your insulation is (a lot of older construction in the Bay Area has really poor insulation; after all, we don't have to deal with harsh winters). That said, when it gets really bad outside (AQI >150) for over a few days, it's almost certainly going to get bad inside if you don't have any filtration.

One thing worth mentioning though is that the smoke you smell is volatile organic compounds, and the smoke you see is (I believe) PM10. You're not going to smell or see PM2.5, which is what these HEPA air purifiers are designed to filter. I'm not confident in this, but my intuition is that these smaller PM2.5 particles will find their way into your home more more quickly than the larger PM10 particles will.