Everyone loves free stuff. I do too!
In fact, the most popular online invitation service in the US offers free options, and that, along with their seniority, is why they are widely used. But the labor, web hosting, and maintenance that goes into an online invite has to be paid for by something. And 9 times out of 10, that something is ADS.
What's wrong with ads? If they make things free for me, they're actually good, right?