Your statement is not exactly true. “regardless of how much it cost to rebuild, they’ll pay for it. No chance of being under insured.”
You may find a host of items that need additional riders to cover ylou. IE Wedding rings and jewlery, gun collections, expensive rugs.
WIth respect to building cost usually the policy will allow you to go up to 125% of the value.
Now if you did significant upgrades to your kitchen with Granite Countertops and stainless appliances you need to inform your insurance company. Same is true if you added expensive hardwood floors.
Pretty easy to esceed the value of the policy.
My suggestion to alll is get your video camera out and film your house and send a copy to your agent as backup if anything ever appens.