Why is probability limited to numbers between 0 and 1?

It is limited because probability is always positive.

0 means something will not happen is impossible

1 means something will happen.

There are no other options above or below.

It will happen or it wont or it is more or less likely to happen aka the numbers between.

View it as being unsure or sure, being unsure which is 0% sure

and being 100% sure.

You can be 5% or 75% sure but being 110% is not actually possible.