On the average, half of the last page in a program will be wasted. Since the unused bytes in a page occupy space in a page frame when the page is loaded, we would like to minimize the waste, and this drives us toward smaller page sizes. Similarly, we find that the first and last pages in each part of the working set generate some waste, driving us to smaller pages. Smalller pages waste less main memory. However, each page requires a page table entry.
Smaller pages mean more pages, and so more page table entries.
Further, larger pages use I-O more effectively than smaller pages. As with much of the rest of computer architecture, the designer is faced with a set of trade-offs.