If you're thinking of the 'Contracts' page on the wiki, almost none of them use tx-replacement, and the ones that did were insecure because tx replacement is just another type of zero-conf transaction. For micropayments specifically a much better and secure mechanism that doesn't use tx-replacement was developed and is what bitcoinj implements.

Note that nLockTime'd transactions are only non-standard until the locktime expires, at which point they can be broadcast and mined normally.

Frankly nSequence-based replacement shows that Satoshi was human just like the rest of us... it's an awful mechanism that just can't be made secure and opens up DoS attacks if you try.