User blog comment:Kaido King of the Beasts/Chapter 868: Eye to Eye, No Conversation (In an Mmmbop They're Gone)/@comment-103.14.60.62-20170610131801/@comment-25161930-20170612163208

Probably the fruit's limits. Maybe he can produce some of it and it tires him like the Ope Ope no Mi, or maybe something about the food quality, after all they went to a island with fruit when her eldest dougther is the minister of fruit, so obviously that island's fruit has something special to them. All we saw Streusen using his power for is log into meat so maybe he can't produce flour just wheat. Maybe he can only turn stuff once so anything on Whole Cake Island that he already used his power on is out (since almost the entire island is eatible that would mean pretty much anything was affected by him) so they had to be aquired elsewhere. Maybe those islands were late on their payment for Big Mom so two birds one stone... Take your pick.