The cost is absolutely not prohibitive, it's about $1-2/sq ft in a new home or $5-6/sq ft if you're retrofitting an old home[1]. For a new 2000 sq ft house that would be around $4000 dollars. Probably <1% of the overall house value given recent housing prices.

[1] https://www.bobvila.com/articles/465-residential-sprinkler-s...

This would depend on house prices. Where I live, you can buy a 2000 sq ft house for $300K or less. That's 1.3% increase in price to add sprinklers, and I would wager that 99% of homeowners would prefer not to spend $4K on this.

California is a big EV market. Sprinklers are required in new construction in CA.

https://www.nahb.org/-/media/NAHB/advocacy/docs/top-prioriti...

Your link shows that 48 out of 50 states don't require sprinklers. I would guess that less than 5% of SFR in the US have sprinklers.

>Your link shows that 48 out of 50 states don't require sprinklers.

Partial Mandate: NY, Mass Full Mandate: CA, Maryland

Those are 2 big states in there. By population the four are ~73 million, or a fifth of America.

Massachusetts only requires them in townhomes and houses over 14K square feet. In other words mansions. NY only requires them in three story buildings, otherwise it's up to the buyer. So these are nonsense arguments. Considering how many existing houses are exempt from all of this, I would estimate that less than 10% of the homes in CA have them, and less than 2% in these other four states.

All post 2018 construction in my area (including single family residential) is required to have automatic sprinklers).