They already have a small army of salespeople pushing their ad network to SMB. Extending their salespeople's product line to include 'offers' wouldn't be a huge stretch.
In one, google was the first, the inventor if you like, and gathered the customer base slowly, in the other, they have competition, are late to the game, and probably besides tech savy people who read hacker news or other tech magazines very few people would know that Google Offers even exists without some massive ad campaign.
