Internationals are THE big stumbling block, not just because of the lack of them - RU whether you love or detest it has the World Cup, Six Nations and Autumn Internationals, where you know the dates, teams, format and good idea of who will be covering it fairly early. Then you have RL with a World Cup where you're unsure about the teams, unsure about how much mainstream media attention it will get and possibly unsure whether it will actually happen at all. Then you have the international scene outside the WC where it appears the Wheelchair teams are working harder to play more matches than the Men's do.
But also, the issue for me with RL is look WHO the nations being targeted are. RU's World Cup gets coverage in lots of rich or at least middling markets - UK, Australasia, North America, Japan, I'm sure mainland Europe is covered too.
What does RL have instead? Cook Islands with a worldwide community of roughly 120,000, Fiji Samoa and Tonga who are less than a million combined and Lebanon which is an economic basket case. Why is a blue-chip company going to want to invest in sponsorship for exposure in Rarotonga and Beirut when they can punp money into the other code and get viewers in L.A. and Tokyo?