What's the use of contracts if wrestlers are allowed to leave anytime they want? [closed]

What's the use of contracts in professional wrestling TV shows if wrestlers are allowed to leave anytime they want?

You seem to be actually asking a different question which is why was he "allowed" to leave while holding the Championship title.

Firstly, a contract is just that, an agreement with legal penalties written in. No one is "forced" to work.

The wrestler is free to leave at any time BUT there may (and usually are) legal requirements he MUST observe if he does. They usually involve (but are not limited to) non-compete clauses, financial penalties and hush clauses etc.

As to your implied question:

We do not know the terms of Benoit's contract or the details of his leaving WCW but it's clear WCW expected him to renew his contract (or they would not have hung the title on him) but couldn't come to terms with him and so he left.

Benoit was unhappy working for WCW. One last attempt in January 2000 was made to try to keep him with WCW, by putting the vacant WCW World Heavyweight Championship on him by defeating Sid Vicious at Souled Out. However, due to disagreements with management and to protest the promotion of Kevin Sullivan to head booker, Benoit left the company the next day alongside his friends Eddie Guerrero, Dean Malenko, and Perry Saturn, forfeiting his title in the process.

Wikipedia