We are not privy to why, or why not, Apple does things certain ways. For one, unless Apple decides that the account is in violation of its terms then they may not even close it and your address is blocked because it is still in use.
Even if the account is closed, this probably applies:
From: https://support.apple.com/102559
“Can I use the primary email address for my deleted Apple Account to create a new Apple Account or with another existing Apple Account?
No, once your Apple Account is deleted, you can’t use the email address that you used with it to create a new Apple Account for as long as Apple retains the one-way hash of the email address. For third-party (non-Apple) domain accounts, the one-way hash is deleted after six years. For other accounts, this is retained according to Apple's retention policy, which is reviewed regularly. In addition, you can’t use that email address with another existing Apple Account except as a rescue email. Also, if your primary Apple Account email address is with a Custom Email Domain, it can never be reused to create an Apple Account after your Apple Account is deleted, even if the domain ownership changes.”