[DannyBee]

We actually do tolerate it. Plenty of critical parts in your car are designed to not be 100% available even in all expected cases.

For example, plenty of higher end cars in california come with summer tires that can't be used in cold weather/ice.

Even the brakes you are talking about must be replaced every X miles (depending on how new the car is, this may be between 10k and 50k miles)

Houses are not definitely designed to be 100% available. This is in fact why they fail due to fire or earthquake or other events. The design point is not instant failure, but it's also not "100% available".

Like the SRE book says, they make a tradeoff.