Engagement entails much more than rote repetition of a procedure. Math worksheets tend to present very similar problem types over and over, leading to mundane practice of disassociated skills. For students who understand the material and successfully complete an assignment, another worksheet becomes meaningless. On the other hand, for the students who don't understand the material, an alternative method of instruction is what's needed. Another worksheet simply adds to the student's frustration, or worse, contributes to a belief that "I'll never understand math." A cute image or a "fill_in_the_blanks" riddle does nothing to increase engagement or learning (and let's face it, those riddles are not funny!). Instead, teachers need to increase engagement by providing students with exercises in which they discover patterns and relationships, solve problems, or think creatively about math relationships.
It is amazing the difference in effort you will get from worksheet to worksheet. Granted the amount of effort may vary immensely from year to year depending on the group of students you have. However for the most part, when a worksheet is needed to help drill down a procedure, standard, or lesson, its effectiveness can and will vary. Therefore it is our job as the teacher to make sure that when we need to utilize a worksheet, we provide the students with one that is as inspiring as can be. Times are different these days. Kids are growing up in a world of microwaves, fast food chains, Nintendo, Wifi, iPads, along with a ton of other technical marvels. When I was growing up we didn't have home computers let alone PlayStation to entertain ourselves. Handheld camcorders were barely coming to the retail market by the time I was in 8th grade, but still a long ways away from the YouTube and Facebook arena we now see today. Times were extremely different back then and so was school.