Because that seems to be the approach with Royal Court and, as I described in that other thread I linked, it makes the mechanic feel less connected and less fun if it's just a disconnected benefit with no real drawback mechanically integrated into the game. You aren't forced to hold court, despite the logical reasons why you would be expected as a monarch to hold court, and because of that it feels like a tacked on event window that you can optionally engage in instead of an integral part of ruling your kingdom.
I've seen the comparison between tours and holding court a few times, and I feel the comparison is not an especially useful one to make, because how they operate is significantly different. We can look at feasts to see how they differ.
Feasts are a useful tool for a variety of situations. Firstly, feasts can relieve stress, something that many rulers constantly have to deal with. Secondly, feasts grant you prestige, and one of the few ways to convert gold into prestige when at peace. Finally, feasts grant opinion bonuses to all who attend, making them a useful first activity to a new lord who wants to counteract that new ruler penalty. Now, there are several different events that can happen at a feast, but you know that you can count on feasts to help out with these issues at the very least. Feasts are a tool your ruler can use.
Compare this to holding court. When you hold court, you don't know what problems you're solving. It's not a reliable tool for anything. All that you know is that you are going to get 3 random events, and that's it. Now, those 3 random events might help fix problems your currently dealing with, or present new opportunities for you to exploit, but they also might be entirely irrelevant or occasionally even harmful. You can't count on holding court to help you with any specific problem, making it not a useful tool for your ruler.
Now if we look at tours, they hew far, far closer to feasts then holding court. While we don't know exactly how tours will work, we do some details. We know you can choose which vassals you want to visit. We know you can choose your intent for the tour, specifying what you want to get out of it. While we don't know most of the events that will surround tours or how effective they will be, we do know what problems they will help with. This makes tours a useful tool, where you can see a problem ,like say lack of gold, and use a taxes tour to help fix that problem.
Also, viewing tours in this light helps explain why it doesn't automatically need a negative enforcement mechanic associated with it. It's a tool to solve problems, but it shouldn't be the only way to solve a problem. Of course, this does cause some slight problems where the player will be able to better make use of tours then the AI, but that is true for nearly every single mechanic in the game and tours are probably not the best place to address this imbalance.