Well, function implies form in this universe to some degree. The more functions we want to put into a machine the more it's form is constrained. If we want some

Well, function implies form in this universe to some degree. The more functions we want to put into a machine the more it's form is constrained. If we want something that does all what birds do .. we need to build a bird. That said we already have drones. We can add a charging station, an artificial beak, a speaker and it can do bird stuff pretty well :) What we suck at is building self-replicators. Cats are considered better vermin hunters than simple machines, like rat traps, because they have a lot of extra benefits of being household pets. (Which rat traps don't do well. Also usually dogs are used to hunt vermin. [I wanted to find that video where dogs hunt on the field as a tractor plows it, but only found this about minks :o https://www.youtube.com/watch?v=MB1I7UixASY https://www.youtube.com/watch?v=MB1I7UixASY ].) Fish tank cleaning is also a very specific problem. It's basically a niche. If we look at it as an engineering challenge it's a hard problem. Small space, hard to reach spaces, mostly mechanical work is needed (as fish tank life is very sensitive to water quality), etc. And there's also cost. It's very possible that if we were to spend a few billion dollars on the problem we could come up with a fish tank cleaner, but ... snails are provided by evolution for free.