There are several reasons why students may struggle with blending. One reason is that they haven't had enough practice. Another reason might be that they don't understand how blends work; they may need some explicit instruction on how to blend sounds together. Additionally, some students may have difficulty hearing the individual sounds in words, which makes it difficult to blend them together. Finally, some students simply find blending to be a difficult skill; it doesn't come naturally to everyone. With some practice and patience, most students can learn to blend words effectively.