Why people fall into these categories, however, is a mystery.

This is the reason why I didn't come yesterday.

Why don't you polish the shoes with this cloth?

Why don't you try on this yellow sweater?

Why don't we talk over coffee?

Why did you come here this morning?

Why did he quit his job?

Why wouldn't you listen to his advice?

Why don't we have dinner together?

Why don't you try a new hobby?