Why do you think that is? I think it's because method syntax fits more neatly into the larger C# paradigm of imperative code. Using both requires the developer to pivot to a different mental model (declarative coding), so we try to standardize on the one that fits best in the bigger picture. This is what I mean by cognitive load. Most devs can surely handle both, but why make them do extra mental work when that effort is better spent on the problem domain.