Why do some surveys involve product offers, free trials, etc.?

Some market research companies and/or the big companies they represent work with various sponsors, promotional companies, etc. And sometimes you'll be invited to purchase products at a discount, participate in trial offers, etc. You can safely ignore these offers if you're not interested.

The reason some of them do this is two-fold - it's a way to help promote their products and services, and it's also used to help offset the cost of paying high rewards to survey participants. You'll notice that these are usually the ones that pay the highest rewards, but you can still ignore the offers.