Assume every motor has a 1% failure rate per year.
A boring wheeled roomba has 3 motors. That's a 2.9% failure rate per year, and 8.6% failures over 3 years.
Assume a humanoid robot has 43 motors. That gives you a 35% failure rate per year, and 73% over 3 years. That ain't good.
And not only is the humanoid robot less reliable, it's also 14.3x the price - because it's got 14.3x as many motors in it.
[1] And bearings and encoders and gearboxes and control boards and stuff... but they're largely proportional to the number of motors.
For example, an industrial robot arm with 6 motors achieves much higher reliability than a consumer roomba with 3 motors. They do this with more metal parts, more precision machining, much more generous design tolerances, and suchlike. Which they can afford by charging 100x as much per unit.
For example, if you're making a phone that is going to be sold around the world, then you're going to worry about arctic/equator temps (will some of your components melt or ICs fail), salty sea air (will the product begin to corrode for people living by a beach), or fast moving elevators (will the speakers pop from a sudden change in pressure).
You can check out this manufacturers robot arms as some examples of existing products. They list some data sheets for their robot arms, including some arms that are IPxx rated. I don't think looking at robot arms is a 1to1 comparison for what you could expect from a humanoid robot since the considerations in the design process are going to be different.
website is kuka dot com/en-at/products/robotics-systems/industrial-robots/kr-agilus