The problem is that OpenSSL's API itself is quite complicated and probably not in an entirely necessary way. As but one concrete example, there's almost no particularly satisfying way to handle the "error queue" in a world with imperfect software. I also recently found how how insanely impractical it is in practice to perform one's own certificate validation (e.g. so I could interpret the CN field) if a TLS connection is abstracted even a tiny bit (e.g. in a database driver).

Little doubt that someone would find it useful, but it is An Undertaking, to preserve something which is not that desirable.