It's the most practical way. Two legs allows smooth and fast running, and I guess the only thing that would be variable is number of arms, fingers, eyes, etc.
Two legs?
Two legs are not the fastest thing in the world.
In fact, we are a lot less balanced in some ways.
Ever heard of a cheetah?
Birds can fly.
Being able to have "smooth and fast running" is completely irrelevant, anyway.
Life can have a completely different setup to accommodate its needs for energy. Think from the very bottom. Will arms, legs, eyes, fingers, will they evolve in every environment, evolve the same way?
The human hand is one of our defining characteristics. It can grip things very effectively.
There are innumerable other ways that good handling can be made.
Imagine a tentacle with a tentacle spiraling out near the end, making a sort of grip.
Or, perhaps, like the Eosapien, tentacle-like "fingers" that can grip things in ways far different than the human way.
Octopus tentacles grip things very strongly and perhaps very finely, perhaps even more finely with some tuning.
you can always substitute arms for legs
What if there were no legs to begin with? What if it was an aquatic ecosystem that had no legs in the first place? What if manipulation came from other places, a tail, perhaps, there are many, many, many ways things can work.
If you're an intelligent, tool-using terrestrial animal, you have no need for more than two legs. It's just unneeded for someone who doesn't need to physically catch their food.
Again, you're basing all life off of chordates.
Then nothing's stopping a creature with 7 eyes and 4 arms and razor-sharp teeth from coming into existence.
There is their environment, but if their environment favors such qualities, they sure as hell can develop them.