You could, but you'd still have a similar problem. Imagine that footraces all had to be run in the same model shoes, in whatever size.
Human body variation far exceeds any kind of standard sizing. There's a reason that anything that fits a body often has hundreds of different competing designs and materials and size specs and different people are more comfortable with different ones.
It's bordering intractable to try to make a "standard" bike that fits the full variation of human bodies. Making that a requirement for a race would favor people who happen to have bodies more congruent with whatever your geometry and materials and sizing quantum are.
Human body variation far exceeds any kind of standard sizing. There's a reason that anything that fits a body often has hundreds of different competing designs and materials and size specs and different people are more comfortable with different ones.
It's bordering intractable to try to make a "standard" bike that fits the full variation of human bodies. Making that a requirement for a race would favor people who happen to have bodies more congruent with whatever your geometry and materials and sizing quantum are.