What you probably did was to qualify for the "Vegas Qualifier", or "World Qualifier" which happens once each year prior to the Team Championships each August in Las Vegas. You probably won the Tri-Cup, or Tri-annual, whatever it's called in your area. And just as you, and the other players on your team, had to achieve a specific number of matches to be eligible for playoffs, including the Tri-Cup, and including the Vegas Qualifier, you need to be on an active roster to qualify for play in any tournaments based upon league play.
Please read, and re-read the above. It's on you, and/or your team captain, to be aware of the rules, and abide by them. This includes whatever local by-laws exist for your league. These rules and by-laws are available to you, and your team members, so read and understand them. Game rules are detailed, but most end up earning about a rule after being burned by it. The Team Manual is available here:
Get familiar with the sections preceding the game rules too. It'll only help you.
When I'm asked for the logic behind some rules or requirements, this is my standard answer. It's the same for all the other leagues to one extent or another. The business model is genius when you view it from that perspective, and they truly do enforce the rules at the higher level competitions, even if your local league matches don't. The benefit of qualifying for the higher level, or advanced tournaments, along with the things that go along with those qualifications, also require your continued participation. They are not "open" tournaments.