It seems like evolution to me. They came to Earth about 10 years ago, and humans took care of them. Generation after generation, they began to adopt human technology, characteristics, and practices, such as attending school, brushing their teeth, gambling, playing instruments, playing with toys, reproduction rituals, etc. It's fun to spend a week or two with a P1, then take a look at the V4s and see how much the Tamagotchi species has come as a whole in 10 short years, no? But no matter what, they're always dependent on the human race for care and guidance.
This is an interesting topic!
The background story to Tamagotchis has never changed, although they seem to emphasize it less with the newer versions: They are aliens who discover Earth, and in an effort to learn about us, send a ship to Earth which crash lands. A Professor and his assistant find the crashed aliens, and put them in little protective eggs so they can better survive our atmosphere, and thus Tamagotchis are born.
The Tamagotchi aliens the themselves seem to have changed over time as they learned more about human culture, and now they and their home planet is starting to look more like Earth. Maybe a bizarre form of Westernization?
To me, they always seemed more like an advanced, intelligent species than a pet. After all, they did figure out how to get from their planet to ours somehow, right?
At first, I didn't like the new generation Tamagotchis, especially the ones that go to school, etc. But it makes more sense, after some thought. Now, it's more like they live here on Earth, but migrate to school/work until they eventually decide to move back to their home planet, instead of being stuck here as bored adults just waiting to get fed every day.
But what's weird to me, is how does this advanced alien race that creates efficient space travel not understand the concept of potty training? I know Tamagotchi isn't meant to be taken super seriously, but it's fun to think about anyway.