why does size of the struct need to be a multiple of the largest alignment of any struct member

Question

I understand the padding that takes place between the members of a struct to ensure correct alignment of individual types. However, why does the data structure have to be a

Answer 1

Because of virtual addressing.

"...aligning a page on a page-sized boundary lets the hardware map a virtual address to a physical address by substituting the higher bits in the address, rather than doing complex arithmetic."

By the way, I found the Wikipedia page on this quite well written.