Every why hath a wherefore.

William Shakespeare (1564-1616): The Comedy of Errors. Act ii. Sc. 2.

Whatever sceptic could inquire for,

For every why he had a wherefore.

Samuel Butler (1600-1680): Hudibras. Part i. Canto i. Line 131.

Happy am I; from care I'm free!

Why ar' n't they all contented like me?

Opera of La Bayadère.

Why thus longing, thus forever sighing

For the far-off, unattain'd, and dim,

While the beautiful all round thee lying

Offers up its low, perpetual hymn?

Harriet W. Sewall (1819-1889): Why thus longing?