In D&D 3.x, Wizards had all of the Knowledge skills as class skills. This allowed them to raise their int to very high levels while still being able to dump all their skill points into class skills.

In DDO, all the Knowledge skills got removed, but no other skills were made Wizard class skills to compensate. As a result, Wizards cannot raise their int modifier above +1 (+0 if human) without being forced to dump skill points into cross-class skills.

Very poor design choice.