Sports are so lucrative for the reasons you mention (huge ad revenue). But you fail to mention the reason the ad revenues are so high. People don't Tivo sports. Sure some people do, but for the most part people want to watch sports live. This is why ad revenue is so high.
Football (Soccer) has struggled to get a TV footing in the states, and has only now just begun to do so. There are two main strategies for monetizing football games here:
Put your match on cable. This is the primary strategy, the ESPN networks, Fox Soccer channel and other cable TV channels do not rely as heavily on advertising as the "over the air" networks (ABC/CBS/FOX/NBC) do. This is because they get a significant chunk of their money directly from cable companies. Most channels that go heavy on soccer programming will be in a sports tier package that costs the subscriber more money because it costs the cable company more money.
Get some sponsors. When matches began airing in the US commercial free on non-cable TV (my first recollection of this was the 94 WC in the states, but that's probably because it's the first one I watched) they got companies to sponsor an entire half, or part of a half. They showed their logo next to the score and probably did some voice promotions.
Air your tournament both OTA and on cable. If you're a big company like Disney (ABC + ESPN family of networks), you might have both OTA providers and cable providers. That means you can air some games on your OTA networks and others on pay cable. This is what Disney does with the World Cup, many games are on ESPN and some marquee matches are on ABC. This provides access, but also protection for your OTA network, all of their time slots are not consumed by ad-less TV.
Most of the time you're going to see both of these strategies used. Even the cable networks use integrated advertisements during the half. Part of the reason you don't see more games on live OTA TV in the US is because it's currently hard to monetize and only appeals to a small subset of the American audience, this subset is willing to at least pay for EPSN and probably even pay for a higher sports tier cable plan so they monetize this way.
This all combines to result in football being a far less lucrative sport for the networks than the easier to monetize baseball, basketball, ice hockey and American football. You don't see multi-billion dollar soccer contracts yet, and until they figure out a better way to monetize it in the US they won't.