This seems to be all over the place. It's a real performance killer, and fairly useless. These should be rewritten as simply
WHERE field LIKE "string"
LOWER is implied in all LIKE comparisons, but LIKE without LOWER is way way way more efficient .
My simple tests show it to be 4700% faster
IMO the query engine should be smart enough to spot this, but apparently it isn't, so we should rewrite our queries.