It could be that the Evoker mindset lends itself to a focus on the caster personally being the one doing the blasting; V was pretty mad for a second when she had to use the dominated kobold and Z mocked her for it. Aarindarius could've very well passed down the mindset that real powerful wizards blast their opponents personally and that hiding behind summons is weak. This attitude doesn't even seem to be uncommon, it came up in the exchange between Redcloak and Thanh as well.

Though I like the cleaning up poop theory.