During a deal-making boom, companies can be persuaded to do things that are daring, novel—even slightly crazy. The $18 billion merger of insurance broker Willis and benefits expert Towers Watson is none of these. It is merely as uninspiring as the phrase “professional-services megadeal” sounds.

Willis is playing catch-up with Aon and Marsh & McLennan, the two other leading insurance brokers that expanded into human resources and benefits consulting giants via takeovers.