[tmx]

> no sane client would ever use them

Unfortunately, that's not the case. From RFC 5246:

  Note: some server implementations are known to implement version
  negotiation incorrectly.  For example, there are buggy TLS 1.0
  servers that simply close the connection when the client offers a
  version newer than TLS 1.0.  Also, it is known that some servers will
  refuse the connection if any TLS extensions are included in
  ClientHello.  Interoperability with such buggy servers is a complex
  topic beyond the scope of this document, and may require multiple
  connection attempts by the client.

An attacker that can insert themselves between client and server can cause a negotiation failure - causing the client or server to negotiate a weaker protocol/cipher combination - so its still important to disable weak cipher suites on the server, especially with browsers as old as IE 6 or 7 still kicking around.