Why do we hyphenate between numbers? Example: twenty-six
To avoid ambiguity.
He turned twenty one too many times.
Is not the same as
He turned twenty-one too many times.
This is rather similar to TsSkTo's answer, but why not see another usage?
Can I have twenty-five times?
This asks for the multiple 25 times (some unspecified amount or object) or perhaps it asks for twenty-five records of time.
Can I have twenty five times?
This asks for 100.
The hyphen prevents the former number from becoming an adjective describing the latter one.
EDIT: Changed the word cents to times to better match common usage.