While giving out ton's of likes is nice, we also don't want likes to become invalid either. And there are some badges associated with likes (as well as trust level being associated to it as well). We don't want people to abuse the system to reach these, so a limit was placed (by discourse). While we want people to give likes away to help encourage, we also want them to contain value as well.
Worst case scenario though, you can wait till the next day and like something if you really find there was something you feel deserved it. And I do believe we have a means to lift the limit manually, but @Alexander would need to confirm that.