Because JaronK, while compiling his list of Tiers, placed the Warlock there. He later admitted that he didn't entirely like the warlock, nor really saw it's full potential, and that while warlocks can be tier 3 in certain builds, that those builds don't make the Warlock tier 4. That said he did regard the Warlock as being high(est) tier 4, only just under the Warblade which is regarded as the lowest in Tier 3. he also made a distinction between binders with access to online vestiges (T32) and binders without access to online vestiges (T43).