I always wonder why those robots have to be humanoid.
I swear I don't need a humanoid robot, give me a proper autonomous robot that cleans your house and I'm more than happy. Could be 40 cm tall, and look like a box, I don't care.
But this is all based on the idea we need generic robots when we really need specialized ones.
It's like skipping making kitchen blenders and vacuum cleaners and instead building a robot that will be mixing stuff manually or using a broom.
Manufacturing, where 90% of the process is generally automated has countless specialized ones. It would not make sense to put generic ones there, because humans really are doing very specific work in manufacturing.
Ask a plumber what he thinks about reaching places human reach. Nature tested what exactly? Birds and spiders are sub optimal?
Birds and spiders are much smaller than humans, see point 1. It's unlikely that a bird, spider, or even a rat will be able to cook dinner for you.
Birds are much better at being dinner. The most "successful" bird by a very wide margin is the broiler chicken.
Of the individual animals that are the same scale as humans, the vast majority exist either to be eaten by humans, serve humans, or be cute for humans.
The most successful wild animals of a similar size to humans have 10s of millions of individuals, not billions. Seals for example thrive by existing in places that humans are not suited for.
1 is the real reason. 2 is really down to things like a big brain and opposable thumbs. Our trunk/legs are evolved for persistence hunting and long distance walking - activities that drive approximately 0% of the economy at this point. If robots didn't have to navigate an environment built for bipeds, other configurations would be far more reliable/efficient.
For instance: a quadruped base can be statically stable in case of power loss - a biped really can't.
“I always wonder why those robots have to be humanoid.“
You are correct to wonder this and almost every use case for a robot will be optimized to a non-human form factor.
Certainly there are tasks - like BJJ training partner - that require a human form factor. Almost everything else, including general, purpose, helper, robot, will be cheaper and more extensible in a non-human form factor.
One of your children remarked that nature has experimented with form factors and humans have won… To which I would point out that the upright, bipedal, form factor arose from the limits of oxygen processing, and heat dissipation… Neither limitation will be encountered in the same way with a robot…
… or perhaps I would point out that nature has, indeed, experimented with form factors and ants won - by a very large margin.
1. The world is designed for humans. If you need to reach the places humans reach then you need to be the same size as a human.
2. Nature has tested many different form factors and the human form dominated the others.