There's a clear benefit and that's to protect the integrity of the return that was e-filed, for example, in case you need to amend that return later, only to find that something has changed either by another user inadvertently or by a subsequent system update.

That is independent of paper or electronic copies everyone should retain on the file as part of their record retention policy.

The IRS technically does not require preparers to retain a copy of the tax return. A list of names / SSNs / main form filed is sufficient to meet the IRS retention requirements.